Invertebrate Palaeontology - · PDF fileInvertebrate Palaeontology and Evolution E.N.K. Clarkson Professor ofPalaeontology DepartmentofGeology University ofEdinburgh Scotland Fourth

InvertebratePalaeontologyand Evolution

ENK ClarksonProfessor of PalaeontologyDepartment of GeologyUniversity of EdinburghScotland

Fourth edition

bBlackwellScience




Fourth edition

bBlackwellScience

copy 1979198619931998 by E N K ClarksonPublished by Blackwell Science Ltda Blackwell Publishing company

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First published 1979 by Unwin Hyman LtdSecond edition 1986Third edition 1993 by Chapman amp HallFourth edition 1998 by Blackwell Science Ltd

10 2008

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In memory ([Prof(-ssor Peter Syllester- Bradley(1913-1978)

Contents

PrefaceMacrofossils on CD-ROM

Part One General Palaeontological Concepts

1 Principles ofpalaeontology11 Introduction12 Occurrence of invertebrate fossils in Phanerozoic rocks

Hard-part preservationSoft-part preservation

13 IJivisions of invertebrate palaeontologyTaxonomy

The species conceptNomenclature and identification of fossil speciesTaxonomic hierarchyUse of statistical methods

PalaeobiologyPalaeoecolobYFunctional morphology growth and form

StratigraphyLithostratigraphyBiostratigraphyChronostratigraphy

BibliographyBooks treatises and synlposiaIndividual papers and other references

2 Evolution and the fossil record21 Introduction22 Darwin the species and natural selection

Inheritance and the source of variationWhere does variation come homSignificance of allelesMutationSpread of mutations through populationsIsolation and species formationGenetic drift gene poolsMolecular genetics and evolutionGene regulation during development

23 Fossil record andmocles of evolution

xvxvi

1

333366889

101213131920202022232325

26262628303233343535373838

viii Contents

MicroevolurionAllopatric speciationHeterochronyTesting rnicroevoJutionary patternsAnalysis of case historiesCo-evolution

MacroevolutionSpecies selectionOrigins of higher taxaRates of evolution adaptive radiations and extinction

24 Competition and its effects25 Summary of palaeontological evolution thcmyBibliography

Books treatises and symposiaIndividual papers and other references

3 Major events in the history of life31 Introduction32 Prokaryotcs and eukaryotcs33 Earliest metazoans

Ediacara E1Una two vieArpointsThe traditional viewMcdusoidsPennatulaceansAnnelidsfossils of unknmvn afllnitiesVendozoan hypothesis

Small shelly f()ssilsPrecambrian trace fossilsCauses of the Cambrian explosion of life

Physicochemical 6ctorsBiological factors

Biological evidence on metazoan relationships34 Major features of the Phanerozoic record

Diversification of invertebrate liteChanges in species diversity and habitatProblematic early Palaeozoic fossilsMarine evolutionary tnmasClimatic and sea-level changesExtinctionsPossible causes of mass extinctions

Earthbound mechanismsExtraterrestrial mechanismsLate Ordovician (Ashgillian) extinction eventLate Devonizlll (Frasnian-Famennian) extinction eventLate Permian extinction eventLate Triassic (Carnian-Norian) extinction eventCretaceous-T ertialY boundary extinction

BibliographyBooks treatises and symposiaIndividual papers and other references

394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

Part Two Invertebrate Phyla

4 Sponges41 Phylum Porifera sponges42 Classification43 Class Demospongea

Spicular demospongesSclerospongesChaetetidsStromatoporoidsSphinctozoans

44 Class Calcarea45 Class Hexactinellida46 Incertae sedis Archaeocyatha

Soft parts organization and ecologyDistribution and stratigraphic use

47 Geological importance of sponges48 Sponge reets

Spicular sponge reetsCalcareous sponge reefs

13ibliographyBooks treatises and symposiaIndividual papers and other references

5 Cnidarians51 Introduction52 M0or characteristics and classes of Phylum Cnidana53 Class Hydrozoa

Order I-IydroidaOrder I-Iydrocorallina

54 Class ScyphozoaJJ Class Anthozoa

Subclass CeriantipathariaSubclass OctocoralliaSubclass Zoantharia corals

Order RugosaOrder TabulataOrder ScleractiniaCoral reetsGeological uses of coralsCorals as colonies the limits of zoantharian evolutionMinor orders


6 Bryozoans61 Introduction62 Two examples of living bryozoans

HowerbarlkiaSmittina

Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents

63 Classiflcation64 Morphology and evolution65 Ecology and distribution

Shallow-vater bryozoansReef-dwelling bryozoansDeep-water byozoans

66 Stratigraphical useBibliography

Books treatises and symposiaIndividu~11 papers and other references

7 Brachiopods71 Introduction72 Morphology

Subphylum RhynchonelliformeaMorphology of three generaPreservation study and classification of articulated brachiopodsM(~or features of brachiopod morphologyEndopunctation and pseudopunctation in shells

Subphylum LingulifonneaLingulaOther Lingulifonnea

Subphylum Craniitormea73 Ontogeny74 Classification75 Evolutionary history76 Ecology and distribution

Ecol06ry of individual speciesEpi6unal brachiopodsEndofaunal brachiopods

Brachiopod assemblages and community ecologyOrdovician palaeocommunitiesSilurian palaeocommunitiesDevonian brachiopod assemblagesPermian reef associationsMesozoic brachiopod associations

77 Faunal provinces78 Stratigraphical useBibliography


8 Molluscs81 Fundamental organization82 Classification83 Some aspects of shell morphology and growth

Coiled shell morphologySeptation of the shell

84 Principal fossil groupsClass Bivalvia

147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203

CerastodernwRange of form and structure in bivalvesClassificationEvolutionary historyFunctional morphology and ecologyEcology and palaeoecologyStratigraphical use

Class RostroconchiaClass Gastropoda

Introduction and anatornyClassificationShell structure and morphologyShell compositionEvolution

Class CephalopodaSubclass NautiloideaSubclass AmmonoideaSubclass Coleoidea dibranchiate cephalopods

85 Predation and the evolution of molluscsBibliography


9 Echinodenns91 Introduction92 Classification93 Subphylum Echinozoa

Class EchinoideaMorphology and life habits of three generaClassi ficationSubclass PerischoechinoideaSubclass CidaroideaSubclass Euechinoidea and the morphological characters of euechinoidsEvolution in ecbinoids

Class HolothuroideaClass Edrioasteroidea

lt)4 Subphylum AsterozoaSubclass AsteroideaSubclass SomasteroideaSubclass OphiuroideaStarfish beds

95 Subphylum CrinozoaClass Crinoidea

Main groups of crinOIdsPalaeozoic crinoidsMesozoic to recent crinoids articulatesEcology of crinoidsFormation of crinoidallimestones

96 Subphylum BlastozoaClasses Diploporita and Rhombifera cystoids

Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

Structural char3cteristicsPore structuresClassificationEcology

Class BlastoideaDiversity and tlll1ction of hydrospiresClassification and evolution ofblastoidsEcology and distribution ofblastoids

97 Subphylum Homalozoa otherWIse calcichordates98 Evolution

Earliest echinoderms and their radiationsEvolution of the tube feetWhy pentameryConvergent evolution and intermediate forms


10 Graptolites101 Structure

Order GraptoloideaSacto~raptus chirnaeraDiplograptus eplotheca

Order DendroidejDcndrograptus

Preservation and study of graptolitesUltrastructure and chcmistlY of graptolite periderm

102 ClassifIcation103 Diological atlinities104 Evolution

Shape of graptolite rhabdosomesProxirnal end in graptoloidsThecal structureCladiaStructure of rctiolitids

105 Hmv did graptolites livePassive driftingAutomobilityUse of models in interpreting the mode of life of graptoloids

106 Faunal provinces107 Stratigraphical uscBibliography


11 Arthropods111 Introduction112 Classification and general rnorphology

Diversity of arthropod typesFeatures of arthropod organization

30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349

113 TrilobitaGeneral morphologyIlcastc dOlll1irlgiacDetailed morphology of trilobites

CuticleCephalonGlabellaCephalic suturesHypostomeEyesCephalic fringesEnrollment and coaptative stnlcturesThoraxPygidiurnAppendages

Trilobite tracks and trailsWalking movements in arthropodsDifferent kinds of trilobite trails

Life attitudes habits and ecolo[yEcdysis and ontogenyClassificationEvolution

General pattern of evolutionMicroevolution

Faunal provincesStratigraphical use

114 Phylum ChelicerataClass Merostomata

Subclass XiphosuraSubclass Eurypterida

115 Phylum CrustaceaBibliography

Books treatises and symposiaIndividual papers and other rderences

12 Exceptional faunas ichnology121 Introduction122 Burgess Shale tllma

ArthropodsLobopodsOther invertebratesSignificance of the Burgess Shale faunas

EcologyGeographical distributionDiversityPersistence

123 Upper Cambrian of southern Sweden124 I IUllSrLickschiefer [nma125 Mazon Creek buna126 Solnhofen lithographic limestone Bavaria

Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents

l27 IchnologyClassification of trace fossils

lVlorphological and preservational classificationBehavioural classificationPhylogenetic classification

Uses of lchnolobY)TSedimentary environmentStratigraphyFossil behaviour

BibliographyBooks treatises and symposia (exceptional faunas)Individual papers and other references (exceptional bunas)Books treatises and symposia (ichnol06))Individual papers (ichnology)

Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface

The first three editions of this textbook were pubshylished in 1979 1986 and 1992 and I trust that thisnew one necessitated by so many advances both infact and theory vill retain its function as a coursetext for students of palaeontology from their secondyear onwards I have made substantial changes toChapters 1-378 and 12 and the Trace Fossils secshytion has been transferred from Chapter 1 to the lastchapter All the other chapters have been revised toa greater or lesser extent I have redrawn about halfof the illustrations a singularly congenial occupationflr long winter evenings and I hope that these willprove of value in helping students to understand theanatomy and terminology of f()ssil invertebrates

Key words appear in bold at their first mention inthe text There is no specific index for them butthey appear in the General Index

As before I wish to thank all my fi-iends colshyleagues and family who have given me such assistshyance in preparing this new edition Derek BriggsColin Scrutton and Rachel Wood gave excellentadvice at the beginning of the project as to how Ishould proceed with the fourth edition and I havetaken on board most of their suggestions As alwaysthese colleagues together with David tlarper PeterSheldon Susan Rigby Liz Harper Dick JefferiesJohn Cope Alan Owen and various others havehelped me at all stages and so have many others toonumerous to Inention in my own country andabroad and my thanks are due to all

I would like above all to record my heartfeltthanks to my true and stalwart fi-iend Cecilia Taylorf()l- all the support and helpfill suggestions she has

given me at every stage I Iad Cecilia not undertakenthe vast job of rebuilding our teaching collectionsand preparing new course materials I would neverha ve had the time to complete this book before thedeadline

To lZoisin Moran of University College GalwayI extend my grateful thanks for her two beautifulpaintings for the Part Title pages

I wish to thank also my editorial colleaguesDr Ian Francis and Jane Plowman who have givenall possible assistance From Ian came the suggestionwhich we have followed up that the new editionshould be coupled with a CD-ROM of FossilImages rlllS has been undertaken in cor~unction

with the Natural IIistory Museum London and toNorman McLeod and Paul Taylor of that institutionlowe a great deal I am likewise gratefil1 to DavidHicks and Eve Daintith for their meticulous copyshyediting and proofreading respectively

On a wet November day over SO years ago I wastaken into a museum in my native Newcastle-uponshyTyne to escape fimn the rain There in a dusty glasscase were two giant ammonites (probably TitanitesZigantcus) and I was given to understand that theyhad lived millions ofyears ago They excited a poundscishynation which has continued until now and I am stillglad to escape to the hills on a fj-esh summer mornshying to search for fossils and then to bring them backto the laboratory for study I hope that this bookwill be of value to any student wishing to exploresomething of the richness and diversity of ancientlife and of the methods available for its scientificstudy If so I will have achieved what I set out to do_

Euan ClarksonEdinburgh

PaleoBase-Macrofossilson CD-ROM

The Natural History Museum London and Dr ENK Clarkson have collaborated on the development of thisimportant new initiative in paleontology teaching

PaleoBase is a combined image library and database containing records for 1000 key fossil genera Eachrecord contains a set of images and information on stratigraphic range hard-part mineralogy palaeoecologypalaeobiogeography etc The images have been captured using the Natural History Museums high resolutionPALAEOVISION digital imaging system and the data and images reside in the CompuStrat database manager

This system allows the user great flexibility in displaying data For example users can simply browse fromrecord to record pull up fossils from a taxonomic index or select and sort records by geographic range lifehabit stratigraphic range or by a variety of other criteria Range charts and palaeobiographic maps are givenwhere appropriate and the user can print records or export them into other applications Within each of themajor groups there are a number of labelled images and diagrams to allow the user to become familiiar withkey morphological terms

PaleoBase may be used as an adjunct to Invertebrate Palaeontology or as a standalone product Taxa havebeen selected for their relevance to Earth science teaching worldwide

PC or MAC minimum 8 Mb RAM CD-ROM drive 640 x 480 colour monitor

For fllrther int(mnation aud ordering details please contact ianJimcisCdblackscicouk

PART ONE

General

Palaeontological

Concepts

Amioceras cf hartmanni (Oppel I an assemblage of immature ammonites from the Lower Jurassic of Black Ven Charmouth England(Lower Sinemurian) These specimens were probably catastrophically buried since the soft parts must have been in place when theydied preventing sediment penetrating the chambers Painting by Raisin Moran original specimen in the James Mitchell MuseumUniversity College Galway Ireland

Principies ofpoloeontology

Once upon a time Some 4600 miIlion years ago the Earth came into

being probably forming from a condensing disc ofparticles dust and gas which slowly rotated roundthe Sun Larger particles or planetismals formedfrom this nebular disc and as these collided theyaccreted eventually tanning the planets

Of all the nine planets in the Solar System onlyEarth as f1r as is known supports advanced lifethongh at the time of writing nlUch interest hasbeen generated by the discovery of organic materialon Jupiters satellite Europa It is however a strikshying tact that life on Earth began very early indeedwithin the first 30 of the planets history Thereare remains of simple organisms (bacteria and blueshygreen algae or cyanobacteria) in rocks 3400 111aold so Ii fe presumably originated before thenThese simple tlt)fJm of life seem to have dominatedthe scene for the next 2000 Ma and evolutionat that time was very slow Nevertheless thecyanobacteria and photosynthetic bacteria wereinstrumental in changing the environment for theygave off oxygen into an atmosphere that was previshyously devoid of it so that animal life eventuallybecame possible

Only when some of the early living beings of thisEarth had reached a high level of physiological andreproductive organization (and most particularlywhen sexual reproduction originated) was the rateof evolutionary change accelerated and with it allmanner of new possibilities were opened up toevolving life This was not until comparatively latein geological history and there are no fossil animalsknown from sediments older than about 700 MaNeedless to say these are all invertebrate animalslacking backbones All of them are marine there is

no record of terrestrial animals until much later Interms of our understanding of the history of lifeperhaps the most significant of all events took placeabont 543 Ma ago at about the beginning of theCambrian Period for at this stage there was a sudshyden proliferation of ditferent kinds of marine invershytebrates During this critical period the principalinvertebrate groups were established and they thendiversified and expanded Sonle of these organismsacquired hard shells and were capable of being fosshysilized and only because of this can there be anychance of understanding the history of invertebratelite

The stratified sedimentary rocks laid down sincethe early Cambrian and built up throughout thewhole of Phanerozoic time are distinguished by arich heritage of the fossil remains of the inverteshybrates that evolved throuuh successive historicalb

periods their study is the domain of invertebratepalaeontology and the subject of this book

Hard-port preservation

rossil invertebrates occur in many kinds of sedimenshytary rock deposited in the seas during thePhanerozoic They may be very abundant inlimestones shales siltstones and mudstones but onthe whole are not common In sandstonesSedimentary ironstones may have rich fossilremains Occasionally they are found in some coarserocks such as greywackes and even conglomeratesThe state of preservation of fossils varies greatlydepending on the structure and composition of the

4 Principles of palaeontology

original shell the nature and grain size of the enclosshying sediment the chemical conditions at the time ofsedimentation and the subsequent processes of diashygenesis (chemical and physical changes) takingplace in the rock after deposition

The study of the processes leading to fossilizationis known as taphonomy In most caseS only thehard parts of fossil animals are preserved and forthese to be fossilized rapid burial is normally a preshyrequisite The soft-bodied elements in the E1lll1aand those forms with thin organic shells did notnormally survive diagenesis and hence have left littleor no evidence of their existence other than recordsof their activity in the form of trace fossils What wecan see in the rocks is therefore only a narrow bandin a whole spectrum of the organisms that wereonce living only very rarely have there been foundbeds containing some or all of the soft-bodied eleshyments in the fauna as well These arc immensely sigshynificant for palaeontolobry

The oldest such fauna is of late Precambrian agesome 615 Ma old and is our only record of animallife before the Cambrian Another such window isknown in Middle Cambrian rocks from BritishColumbia vhere in addition to the normallyexpected trilobites and brachiopods there is a greatrange of soft-bodied and thin-shelled animals shysponges wonns jellyfish small shrimp-like creashytures and animals of quite unknown affinities shywhich are the only trace of a diverse f2una whichwould otherwise be quite unknovvn (Chapter 12)There arc similar windows at other levels in thegeological column likewise illuminating

The f()ssil record is as a guide to the evolution ofancient life unquestionably limited patchy andincomplete Usually only the hard-shelled elementsin the biota (apart from trace f()ssils) arc preservedand the fossil assemblages present in the rock mayhave been transported some distance abraded damshyaged and mixed with elements of other Elllnas Evenif thick-shelled animals were oribrinally present in afauna they may not be preserved in sandy sedishyments in which the circulating waters are acidic forinstance calcareous shells may dissolve withill a fewyears bef()re the sediment is compacted into rockSince the sea floor is not ahvays a region of continushyous sediment deposition 111any apparently continushyous sedinlentary sequences contain nUlTleroussmall-scale breaks (diastems) representing periodsof winnowing and erosion Any shells on the sea

floor during these erosion periods would probablybe transported or destroyed - another limitation onthe adequacy of the fossil record

On the other hand some 1nari ne invertebratesfound in certain rock types have been preservedabundantly and in exquisite detail so that it is possishyble to infer much about their biology hom theirremains Many of the best-preserved fossils comefl-om limestones or from silty sediments vvith a highcalcareous content In these (Fig 11) the originalcalcareous shells may be retained in the t()ssil statevith relatively little alteration depending upon thechemical conditions within the sediment at the timeof deposition and after

A sediI11ent often consists of components derivedfrom vanous environments and when all of theseincluding decaying organisms dead shells and sedishymentary particles are thrown together the chemicalbalance is unstable The sediment will be in chemishycal equilibriunl only after diagenetic physicochemishycal alterations have taken place These may involverec1)7stallization and the growth of new minerals(authigenesis) as well as cementation and comshypaction of the rock (lithification) and during anyone of these processes the fossils may be altered ordestroyed Shells that are originally of calcite preshyserve best aragonite is a less stable form of calciumcarbonate secreted by certain living organisms (egcorals) and is often recrystallized to calcite duringdiagenesis or dissolved away completely

Calcareous skeletons preserved in more sandy orsilty sediments may dissolve after the sediment hashardened or during weathering of the rock longafter its induration Moulds (often miscalled casts)of the external and internal suliaces of the fossil maybe left and if the sediment is fine enough the detailsthese show may be very good Some methods forthe study of such moulds are described in section72 with reference to brachiopods If a fossilencloses an originally hollow space as for instancebetween the pair of shells of a bivalve or brachioshypod this space may either be lett empty or becomefilled with sediment In the latter case a sedirnentcore is preserved which comes out intact when therock is cracked open This bears upon its surfclCe aninternal mould of the fossil shell whereas extershynal moulds arc left in the clVity tram which itcame In rare circumstances the core or the shell orboth may be replaced by an entirely different minshyeraI as happens in fossils preserved in ironstones If

Occurrence of invertebrate fossils in Phanerozoic rocks 5

recrystallized calcite

~~

(f)

core ---+j

(j)

Ironstone --~~~8B1

Figure 11 possible processes of fossilization of a bivalve shell (a) original shell buried in mud (left) or carbonate (right) (b) theshell was calcite was buried in a carbonate sediment and was preserved intact other than as a small crystallized patch (c) shell origshyinally of aragonite now recrystallized to calcite which destroys the fine structure (d) original calcite shell retained surrounding a diashygenetic core of silica (e) a silica rim grawing on the outside of the shell (f) tectonic distortion of a shell preserved in mudstone (glshell preserved in mud with original shell material leached away leaving an external and an internal mould surrounding a mudstonecore (h) a calcareous concretion growing round the shell and inside (if the original cavity was empty) with patches of pyrite in places(jl ironstone replacement of core and part of shell

the original spaces in the shell are impregnated withextra minerals it is said to be permineralizedwhile the growth of secondary minerals at theexpense of the shell is replacement Cores maysometimes be of pyrite Graptolites are often preshyserved like this anaeorbic decay having releasedhydrogen sulphide which reacted with ferrous(Fe2+) ions in the water to allow an internal pyriteCOle to form Sometimes a core of silica is ()undwithin an unaltered calcite shell This has happenedwith some of the Cretaceous sea urchins of southernEngland They lived in or on a sediment of calcareshy(ms mud along with many sponges which secretedspicules of biogenic silica as a skeleton In alkalineconditions (above pH 9) which may sometimes begenerated during bacterial decay the solubility of

the silica increases markedly and the silica soreleased will travel through the rock and precipitatewherever the pH is lower The inside of a sea urchindecaying under different conditions would trap justsuch all internal microenvironment within whichthe silica could precipitate as a gel Such siliceouscores retain excellent features preserving the intel11a1morphology of the shell On the other hand silicamay replace calcite as a very thin shell over the surshyf~ce of a fossil as a result of SOlTle complex surfacereactions These siliceous crusts may retain a verydetailed expression of the surElce of the fossil andsince they can be treed from the rock by dissolvingthe limestone with hydrochloric acid individualsmall fossils preserved in this way can be studied inthree dimensiollS Some of the most exquisite of all


trilobite and brachiopods are knovl1 from materialsuch as this

A relatively uncommon but exquisite mode ofpreservation is phosphatization Sometimes theexternal skeleton especially of thin organic-shelledanimals may be replaced or overgrown by a thinsheet of phosphate or the latter may reinforce anoriginally phosphatic shelL In the former situationthe external form of the body is precisely replicatedAlternatively a phosphatic filling of the interior ofthe shell may form a core picking out internalstructures in remarkable detail Such preservation isprobably associated with bacterial activity directlyafter the death of the animal Many small Cambrianfossils have been preserved by phosphatization(Chapters 3 and 12) but much larger fossils may bepreserved also for example crustaceans with afluorapatite infilling and with all their delicateappendages intact

Fossils arc often found in concretions calcareshyous or siliceous masses formed around the fossilshortly aiter its death and burial Concretions formunder certain conditions only where a delicatechemical balance exists betveen the water and sedishyment by processes as yet not fully understood

Soft-part preservation

In very rare circumstances soft-bodied organismscan be preserved as fossils and these provide othershywise unobtainable evidence of the diversity of metashyzoans living at particular periods this is discussed inChapter 12

Invertebrate palaeontology is normally studied as asubdivision of geology as it is within Earth scienccthat its greatest applications lie It can also be seen asa biological subject but one that has the unique pershyspective of geological time Within the domain ofinvertebrate palaeontolobY there are a nmnber ofinterrelated topics (Fig 12) all of which have abearing on the others and vhich also link up withother sciences

Three main categories of fossils may be distinshyguished (1) body fossils in other words the actual

remains of some part usually a shell of skeleton of aonce-living organism (2) trace fossils which arctracks trails burrows or other evidcnce of the activshyity of an animal of former timesmiddotmiddot- sometimes theseare the only guide to the former presence of softshybodied animals in a particular environment (3)chemical fossils relics of biogenic organic comshypounds which may be detected geochemically inthe rocks

At the heart of invertebrate palaeontology standstaxonoluy the classification of fossil and modernanimals into ordered and natural groupings Thesegroupings known as taxa must be narned andarranged in a hierarchial system in which their relashytionships are made clear and as pound1r as possible mustbe seen in evolutionary perspective

Evolution theory is compounded ofvarious disshyciplines - pure biology comparative anatomyembryolobry genetics and population biolobY - butit is only the palaeontological aspect that allows thepredictions of evolutionary science to be testedagainst the background of geological time permitsthe tracing of evolving lineages and illustrates someof the patterns of evolution that actually haveoccurred

The rates at which animals have evolved havevaried through time but most animal types(species) have had a geological life of only a ttvvmillion years Some of these evolved rapidly such asthe ammonites others very slowly (Chapter 2) Arock succession of marine sediments built up overmany millions of years may therefore have severalfossil species occurring in a particular sequence eachspecies confined to one part of the succession onlyand representing the time when that species wasliving Herein lies the oldest and Inost general applishycation of invertebrate palaeontolobY biostratigshyraphy Using the sequence of f()ssil faunas thegeological column has been divided up into a seriesof m~~or geological time units (periods) each ofwhich is further divided into a hierarchy of smallunits The whole basis for this historical chronologyis the documented sequence of fossils in the rocksBut different kinds of fossils have different stratishygraphical values and certain parts of the geologicalrecord are more closely subdivided than othersSome absolute ages based on radiometric datinghave been fixed at particular points to this relativescale and these provide a framework for undershystanding the geological record in terms of real time

Divisions of invertebrate palaeontology 7

Figure 12 The various subdisciplines of palaeontology

(ie known periods of millions of years) rather thanas just a purely relative scale This is only possible atcertain horizons however and for practical purshyposes the geological timescale based on biostratigrashyphy is unsurpassed for Phanerozoic sediments

Although stratigraphy is the basis of the primarydiscipline of geochronology a small [lcet ofpalaeontological study has a bearing on what may betermed geochronometry By counting dailygrowth rings in extinct corals and bivalves informashytion has been obtained bearing upon the number ofdays in the lunar month and year in ancient timesThis has helped to confirm geophysical estimates onthe slowing of the Earths rotation (Chapter 5)

Since stratigraphical applications of palaeontologyhave always been so important the nlOre biologicalaspects of palaeontology were relatively neglecteduntil comparatively recently Palaeoecologywhich has developed particularly since the early

1950s is concerned with the relationships of fossilanimals to their environment both as individuals(autecology) and in the faunal communities inwhich they occur naturally the latter is sometimesknown as synecology

Since the soft parts of fossil animals are not norshymally preserved but only their hard shells there arerelatively few ways in which their biology and lifehabits can be understood Studies in functionalmorphology however which deal with the intershypretation of the biology of fossilized skeletons orstructures in terms of their original function havebeen successfully attempted with many kinds of fosshysils restricted in scope though these endeavours maynecessarily be Ichnology is the study of trace fosshysils the tracks surfice trails burrows and boringsmade by once-living animals and preserved in sedishyments This topic has proved valuable both inunderstanding the behaviour of the animals that


lived when the sediment vas being deposited and ininterpreting the contemporaneous environmentFinally it is only by the integration of taxonomicdata on local tltll1as that the global distribution ofmarine invertebrates through time can be elucishydated Such studies of palaeobiogeography (orpalaeozoogeography in the case of aniInals) canbe used in cOl~junction with geophysical data inunderstanding thc former relativc positions andnlovernents of continental rnasses

All of these aspects of pabeontolohY arc interreshylated and an advance in one may have a bearingupon any other Thus a particular study in funcshytional morphology may give intlt-gtrIl1ation onpalaeoecology and possibly some feedback to taxonshyomy as well Likewise recent refinemcnts ill taxoshynomic practice have enabled the development of amuch more precise stratigraphy

Chemical cOlnpounds of biological origin cannow be recovered from ancient rocks and fc)rm thebasis of bionlolecular palaeontology Such fossilnlOlecules may help to diagnose which organismsthey come from and their breakdown patlnvays l11aysay something about the environment l101ecularphylogcnetics based upon protein sequencing mayshow how far two or more related organisms havediverged f1-o111 a cornmon ancestor and to sor11Cextent the available techniques can be applied to therecent fossil record Immunological-determinanttechniques can be used to detect proteins and polyshysaccharides in fossil shells but tor the moment onlyshells younger than 2 Ma have proved anlcnable toanalysis There arc also promising developments alsoin palaeobiochemistry and organic geochemistryvhich are applicable to the fossil record thoughthese arc beyond the scope of this book

Taxonomy

Taxonomy is often undervalued as a glorifiedform offrling - ith each species in its folder likea stamp in its prescribed place in an album buttaxonomy is a fundanlental and dynamic sciencededicated to exploring the causes of relationshipsand similarities among organisms Classificationsare theories about the basis of natural order notdull catalogues compiled only to avoid chaos

The best fnOflOlraphs are works cIgcniu3 (Sj Gould 19(0)

These words should make entirely clear the funshydamental nature of taxonomy For as has often beensaid to identify a fossil correctly is the first step andindeed the key to fmding out further infcHl1utlonabollt it Sound classification and nomenclature lieat the root of all biological and palaeontologicalwork without them no coherent and orderedsysterll of data storage and retrieval is possibleTaxonomy or systematics as it is sometimesknown is the science of classitlcation or organismsIt is the oldest of all the biological disciplines andthe principles outlined by Carl Custav Linnaeus(17CJ7--177H) in his pioneering Systema fwtllrae arestill in use today though greatly modifIed andextended

The species conceptThe fimdarncntal unit of taxonomy is the speciesAnimal species (eg Sylvester-Bradley 1951l) aregroups of individuals that generally look like eachother and can interbreed to produce offlpring of thesame kind They cannot interbreed vith otherspecies Since it is reproductive isolation alone thatddines species it is only really possible to distinguishclosely related species if their breeding habits arcknovn Of all the described species of living anishymals hovever only about a sixth arc gooe orproperly defined species Inf(wI11dtioll upon thereproductive preferences of the other poundi ve-sixths ofall naturally occurring animal populations is just notdocumented

The differentiation of most living and all fossilspecies therefore has to be based upon other andtechnically less valid criteria

Of these by tIl the most important especially inpalaeontology is morphology the SCIence ofform since most natural species tend to be comshyposed of individuals of similar enough externalappearance to be identifiable as of the same kindDistinguishing species of living animals by morphoshylogical criteria alone is not vithout hazards espeshycially where the species in question are sinlilar andclosely related Supplementary information such asthe analysis of species-specific proteins may be ofhelp in some cases where there is good rcason [orit to be sought (eg for disease-carrying insects) Forthe rest some degree of subjectivity in taxonomy hasto be accepted though this can be minimized ifenough morphological criteria arc used

Nomenclature and identification of fossil speciesIn the formal nomenclature of any species living orfossil taxonomists follow the biological system ofLinnaeus whereby each species is defined by twonames the generic and specific (or trivial) namesFor example all cats large and small are relatedand one particular group has been placed in thegenus Felis Of the various species of Felis the speshycific names F catttS F leo and F pardus formallyrefer to the domestic cat lion and leopard respecshytively In full taxonomic nomenclature the authorsname and the date of publication are given after thespecies eg Felis catus (Linnaeus 1778) (see belowfor further discussion)

In palaeontol06Y it can never be known forcertain whether a population with a particular morshyphology was reproductively isolated or not I-Iencethe definition of species in palaeontology as in mostliving specimens must be based almost entirely OIl

morphological criteria Moreover only the hardparts of the fossil animal are preserved and muchuseful data has vanished A careful exarnination anddocumentation of all the anatomical features of thefossil has to be the main guide in establishing thatone specIes is dittcrent from a related species In rarecases this can be supplemented by a comparison ofthe chemistry of the shell as has proved especiallyuseful in the erection of higher taxonomic cateshygories Within any interbreeding population there isusually quite a spread of morphological variationOn a broader scale there may be both geographicaland stratigraphic variations and all these must becarefully documented if the species is to be ideallyestablished Such studies may be very signitlcant inevolutionary palaeontology

When a palaeontologist is attempting to distinshyguish the species in a newly discovered fmna say offossil brachiopods she or he has to separate the indishyvidual fossils out into groups of morphologicallysimilar individuals There may to take an exampleperhaps be eight such groups each distinguished bya particular set of characters Some of these groupsmay be clearly distinct from one another in othersthe distinction may be considerably less increasingthe risk of greater subjectivity These groups areprOVIsionally considered as species which must thenbe identified This is done by consulting palaeontoshylogical monographs or papers containing detailedtechnical descriptions and illustrations of previouslydescribed brachiopod flLInas of similar age and


comparing the species point by point Some of thespecies may prove to be identical with alreadydescribed species or show only minor variation of akind that would be expected in a local variantwithin the same species Other species in the faunamay be new and if so a full technical descriptionwith illustrations must be prepared for each newspecies which should be published in a palaeontoshylogical journal or monograph This description isbased upon type specilllens which are alwaysthereafter kept in a museum or research instituteUsually one of these the holotype is selected asthe reference specimen and fully illustrated COInshyparative detail may be added from other specimenscalled the paratypes There are various other kindsof type specimens for example a neotype may beerected when a holotype has been lost or when aspecies is being redescribed in filller and more upshyto-date terms when no type specimen has previouslybeen designated

A new genus will be designated as gen nov by itsauthor this following the generic name a newspecies as sp nov and a new subspecies as ssp nov

The new species must be named and allocated toan existing genus or if there is no described genusto which it pertains then a new genus must also beerected To appreciate the method let us considerthe following historical tale In the early nineteenthcentury brachiopods were poorly known and fewdistinct genera had been erected One of these wasthe living Terebratula narned by OP Mliller in1776 When EF von Schlotheim first studiedDevonian fossils from North Germany in 1H20 herecognized that some of the shells were brashychiopods and he described one of the most abunshydant fonus as the new species Terebratula sarcinulatusBy 1830 however much more was known aboutbrachiopods and G Fischer de Waldheim proposeda new genus fiJI this species so that it became corshyrectly designated Chonetes sarcinulattts (Schlotheim)This is the type species of Chonetes a well-knownSiluro-Devonian genus of the Class StrophomcnataNote that where a species was originally describedunder a different generic name the original authorsname is quoted in parentheses In 1917 FRCowper Reed then working on Ordovician andSilurian brachiopods of the Girvan district Scotlandrecognized many new species One of these hadsimilarities in rnorphology to Chonetes but it wassuHiciently diHcrent to be regarded as a species of a


new subgenus this is vritten Chonefes (Eochonetes)advena Reed 1917 When in 1928 the taxonomicproblerns of Chonefes and similar forms wereaddressed by OT Jones the nevv SuperfamilyPlectambonitacea was erected to acconllllodateadlJena and many other related brachiopods At alater stage ochonetes was elevated to the rank of afull genus In the most recent treatment DATHarper described a large fauna from the Girvandistrict of Scotland and within this he recognizedtwo subspecies of E advena of somewhat differentages and distinguished by minor differences inmorphology These in Harpers (1989) monographare written Eochonete advena adJena Reed 1917 (desshyignating Reeds original material) and EochomtesadlJeruIReed 1917 Jra cilis ssp nov Subsequentauthors vill refer to the latter in full as FortonetesadlJcrw gracilis Harper 1989 or in abbreviated form asE advena lracilis

Where due to indiHerent preservation or lack ofan up-to-date monographic base a species cannotbe identified with certainty it may be designated asafT (related to) or cf (may be compared vith) anexisting species (eg iVIonolttraptu5 cf lJomerinus)Where the fossil can be identified as belonging to aknown genus but cannot be ascribed to a species (asmay be the case where preservation is poor or ifonly a fiagment is preserved the s_lffix sp (pluralspp) is used (eg Caloceras sp) If the specimen in amore extreme case can only tentatively be referredto a genus one would write eg Kutorgin1 sp Ifonly the species is dubious such an ascription asLoplectodonta pcnkillensis might be used

All taxonomic work such as this must t()llovv aparticular set of rules which have been worked outby a series of International Commissions and aredocumented in full in the opening pages of eachvolume of the Treatise on invertebrate Paleontology (acontinuing series of volumes published by theGeological Society of America)

Taxonomic hierarchyAlthough all taxonomic categories above the specieslevel are to some extent artificial and subjectiveideally they should as far as possible reflect evolushytionary relationships

Similar species arc grouped in genera (singulargenus) genera in fanlilies families in ordersorders in classes and classes in the largest division ofthe animal kingdom phyla (singular phylunl)

There may be various subdivisions of these cateshygories eg superpoundlrnilies suborders etc and in cershytain groups there is even a case for erectingsuperphyla There are only about 30 phyla In theanimal kingdom and only about a dozen of theseeg Mollusca and Brachiopoda leave any fossilre111lt1Il1S

In taxonomy higher taxa are usually distinguishedby their suffix (ie -ea -a etc) As an example thefollowing documents the classification of theOrdovician brachiopod Eochorlctes adlcna gracilisreferred to earlier according to a taxonomic scheInein which the author of the taxon and the year ofpublication are quoted

Phylum Brachiopoda ULlmeril 1806Subphylum Rhynchonelliformea Williams ct al

1996Class StrophomenataWilhams ct al 1996Order Strophomenida ()pik 1934Suborder Strophomenidina Opik1934Superfunily Plectambonitacea Jones 1928Family Sowerbyellidae Opik 1930Subfamily Sowerbyellinae Opik 1930Genus Eochonetes Reed 1917Species advena Reed 1917Subspecies gracilis Harper 1989

In the above section we have seen the divisions ofthe taxonomic hierarchy but in defining thesegroupings how do taxonomists actually go about itThe basic principle is that morphological and othersiluilarities reflect phylogenetic affinity (honlolshyogy) This is always so unless for other reasonssimilarity results from convergent evolution But inassessing similarities how does one decide uponwhich characters are Important How should theybe chosen to minimize subjectivity and producenatural order groups There is no universallyaccepted method of facilitating these ends andtaxonomists have used different rnethods In recentyears three sharply contrasting schools haveemerged these are the schools of (1) evolutionarytaxonomy (2) numerical taxonomy and (3) c1adism

Until the 19705 most palaeontologists especiallythose working with fossil material which they havecollected in the field were evolutionary taxonoshymists In erecting a hierarchical classifIcation suchclassical taxonomists used a traditional and very flexshyible combination of criteria First there is nlorpho-


pound11 the most effective method for reconstructingphylogeny Smiths (1994) explanation of cladisticmethodology is so comprehensive that only briefCOlTunents arc given here

HemTig was of the opinion that recency of comshymon origin could best be shown by the shared posshyseSSIOn of evolutionary novelties or derivedcharacters Thus in closely related groups we wouldsee shared derived characters (synapomorphies)which would distinguish this group from othersHenmgs central concept was that in any groupcharacters arc either primitive (symplesiomorshyphic) or derived Thus all vertebrates have backshybones the possession of a backbone is a primitivecharacter for all vertebrates and is not of courseindicative of any close relationship between anygroup of vertebrates What is a primitive charactertor all vertebrates is of course a derived character ascompared to invertebrates - synapomorphy andsymplesiomorphy thus delineate the relative statusof particular characters with respect to a specificproblem

Hennig endeavoured to provide an objectivemethodology for determining recency of commonorigin in related taxa based upon primitive andderived characters Such relationships arc expressedin a cladogram (Fig 13) in which dichotomousbranching points are arranged in nested hierarchies

Here taxa A and J) share a unique commonancestor They are said to be sister groups Theyboth share an evolutionary novelty or synapomorshyphy not possessed by taxon C Now C is the sistergroup of the combined taxa A and B and D is thesister group of combined taxa A Band C in pershyforming a cladistic analysis therefore a taxonomistassumes that dichotomous splitting had occurredIl1 each lineage and compiles an (unweighted)

Figure 13 A c1adogram (for explanation see text)

logical (or phenetic) resemblance the extent towhich the animals resemble one another Secondphylogenetic relationships are along with pheshynetic resernblancc considered irnportant By this ismeant the way (as Elf as can be determined) inwhich animals are actually related to each other iein terms of recency of common origin which ofcourse grades into evolutionary taxon0111Y Theorder of succession in the rock record and geoshygraphical distribution may play an important part indeciding relationships This prJctical approach totaxonomy which took all factors into considerJtionhas for a long time been the backbone of palaeontoshylogical classitlcation and is still considered to be thebest method by stratophenetic palaeontologists whoplace much emphasis on time in seeking ancestorshydescendant relationships (Henry 1984 Gingerich1990)

For some taxonomists however the uncertaintiesand subjectivity which arc almost inescapable in anykind of c1assitlcation seemed to be particularly acutein classical taxonomy as did the limitations of thefossil record in terms of preservation The numericaltaxonomists tried to escape poundrorn this problem byopting for quantified phenetic resemblance as theonly realistic guide to natural groupings It was theirview that if enough characters were measuredquantitled and computed and represented by the useof cluster statistics the distances between clusterscould be used as a measure of their differencesNumerical taxonomy has been found very usefulin some instances but subjectivity cannot be elimishynated since the operator has to choose (subjectively)how best to analyse the measurements made andmay need to weight them giving certain charactersmore importance (again subjectively) in order toobtain meaningful results Hence the objectivity ofnumerical taxonomy is less than it might appear

The third school relics upon phylogenetic critenaalone emphasizing that features shared by organismsmanifest in nature a hierarchial pattern evident inthe distribution of characters shared amongst organshyisms It is known as cladism or phylogeneticsystelnatics - a school founded by the Germanentomologist Willi Hennig (1966) and was soonapplied vigorously to palaeontology (eg Eldredgeand CrJcraft 1980) In the eJrly days of cladisticsthere were many doubters (including as I have toadmit the present author) But as the method itselfevolved cladistics has come to be recognized as by

A B c D


character data matrix The more characters andcharacter states there are available the larger thedatabase and large databases are often rOlltinelyprocessed and the construction of a cladogramspeeded up by using one of several computer proshygrams The PAUP (Phylogenetic Analysis UsingParsimony) program tor example is a techniquewhich makes the fewest assumptions in ordering a

set of observationsHow can ve distinguish symplcsiolT1orphic

(shared primitive) fi-om synapomorphic (sharedderived) character states The most useful way isoutgroup cornparison Here an ingronp (of whichthe relationships arc under investigation) is specifishycally designated and compared with a closelyrelated middotoutgroup Any character present in a varishyable state in the ingronp must be plesiomorphic ifit is also found in the outgroup Likevise apomorshyphil characters are only present in the ingroup

Hennig distinguished three kinds of cladisticgroupings Monophyletic groups contain the comshymon ancestor and all of its descendants (D C B Ain Fig 13) paraphyletic groups are descendedfrom a common ancestor (usually now extinct andknown as the stem group) but do not include alldescendants (B and C for example in Fig 13)polyphyletic groups on the other hand arc theresult of convergent evolution Their representashytives arc descended from different ancestors andhence although these may look superfIcially similarany polyphyletic group comprising them is artificial

A dadogram is not an evolutionary tree it is ananalysis of relationships As such it is a valuable andrigorous way of working out and showing graphishycally how organisms are related and it forces taxonshyomists to be explicit about patterns and groups Themethodology of cladistics is especially good whendealing with discrete groups with large morphologishycal and stratigraphic gaps and to these it brings thepotential for real objectivity A cladograrn showshow sister groups dre hierarchically related on thebasis of shared-derived homologies but although itportrays taxonomic relationships in ten11S of recencyof common origin the order of succession in therock record is not taken into account (thoughimplicitly cladograms have a tirne axis)

So where does that leave the potential contribushytion of stratigraphy in reconstructing phylogenyWhilst a few transformed cladists negate the valueof the fossil record altogether (3 vievv vigorously

opposed by Ridley 1985) the successive appearanceof taxa in stratigraphy cannot be denied as an essenshytial source of data however imperfect the fossilrecord actually is Thus as Gingerich (1990) comshyments Time is a fundamental dimension in evolushytionary studies and a major goal of palaeontologyshould continue to be the study of the diversificationof major groups in relationship to geological timeSo having constructed an appropriate cladogramthe next stage in exploring relationships is to comshybine this information with biostratigraphic data Forthis Smith (1994) discusses methodology in detailThe result is a phylogenetic tree which shows thesplitting of lineages through time and is efFectivelyabest estimate of the tree oflife Very commonlythere is an excellent correspondence between thecladogram and the rock record on the other handthe combined cladistic and biostratigraphic approachmay throvv up unexpected patterns

The ultimate problem not only tor cladism butfor all taxonomic methodology results ti-om conshyvergent evolution Resemblances in characters orcharacter states may have nothing to do withrecency of comInon orifrin but from convergenceand it may not always be possible to disentangle theresults of the two Thus Willmer (1990) and Mooreand Willmer (1997) in considering the relationshipsbetween major invertebrate groups argue thatcladistic analysis based on parsimony will tend tominimize and thus conceal convergence and theycontend that convergence at all levels is t~lr 1110reimportant than has generally been believed There iscertainly a problem here Even so cladistic methodshyology coupled with biostratigraphy seems to be thebest way f()lward and an essential prerequisite tordrawing up meaningful phylogenetic trees

Use of statistical methodsInevitably palaeontological taxonomy carries a cershytain element of subjectivity since the informationcoded in fossilized shells does not give a completerecord of the structure and life of the animals thatbore them There arc particular complications thatcause trouble For instance palaeontological taxonshyomy can do little to distinguish sibling specieswhich look alike and live in the same area but canshynot interbreed Polymorphic species in whichmany forms arc present within one biologicalspecies may likewise be hard to speciate cOlrectlyIn particular where sexual dimorphism is strong

the males and females of the one species may be sodissirnilar in appearance that they have sornetimesbeen described as different species and the true situshyation may be hard to disentangle (as withammonites Chapter 8)

When it comes to the distinction of closelyrelated species however there are a number of stashytistical tests that may help to give a higher degree ofobjectivity One simple bivariate test in commonuse for example can be used when a series ofgrowth stages are found together If a collection ofbrachiopods is made frarn locality A the lengthwidth ratios or SOIne other appropriate parametersmay be plotted on a graph as a scatter diagranl Aline of best fit (eg a reduced major axis) may thenbe drawn through the scatter This gives a simpley = ax + b graph where a is the gradient and b theintercept on the y axis A similar scatter from a popshyulation collected from locality 13 may be plotted onthe same graph and the reduced major axis drawnfi-om this too The relative slopes and separations ofthe two axes may then be compared statistically Ifthese lie within a certain threshold the populationscan then be regarded as being of the same species ifoutside it then the species are different

This is only one of a whole series of possible testsand more elaborate techniques of multivariateanalysis are becoming increasingly important in taxshyonomic evolutionary studies

With the advent of microcomputers and the proshyvision of specialist software packages designedspecifically to meet the needs of palaeontologists(PALSTAT 13ruton and Harper 1990 Ryan etal 1995) the usc of numerical analysis is beconlingstandard Statistical methods are likewise essentialin defining palaeocommunities in undef()rmingpopulations of det)fmed fossils and comparing themto unaltered rnaterial

Palaeobiology

Various categories may be included in palaeobiolshy0SY palaeoecology (here discussed with palaeobioshygeography) functional morphology and ichnologyeach of which requires some discussion

PalaeoecologySince ecolosY is the study of animals in relation totheir environment palaeoecology is the study of


ancient organisms in their environmental contextAll animals are adapted to their environment in allof its physical chemical and biological aspects Eachspecies is precisely adapted to a particular ecologicalniche in which it feeds and breeds It is the task ofpalaeoecology to fmd out about the nature of theseadaptations in fossil organisms and about the relashytionships of the animals with each other and theirenvironments it involves the exploration of bothpresent and past ecosystems (Schafer 1972)

Although palaeoecology is obviously related toecosystenr ecology it is not and cannot be the sameIn modern community ecology much emphasis isplaced on energy flow through the system but thiskind of determination is just not possible when dealshying with dead communities Instead palaeontologistsperforce must concentrate on establishing the comshyposition structure and organization of palaeocomshymunities in attempting from here to work outlinkage patterns in food webs and in investigatingthe autecology of individual species

Many attempts have been made to summarizecategories of fossil residue to provide the backshyground for interpreting original community strucshyture The scheme proposed by Pickerill and13renchley (1975) and amended by Lockley (1983) isused here

1 An assemblage refers to a single sample trom aparticular horizon

2 An association refers to a group of assemblagesall showing similar recurrent patterns of speciescomposition

3 A palaeocommunity (or fossil community)refers to an assemblage association or group ofassociations mferred to represent a once-distincshytive biological entity Normally this only represhysents the preservable parts of an original biologicalcommunity since the soft-bodied animals are notpreserved This definition corresponds more orless exactly to that of Kauffman and Scott (1976)

Palaeoecology must always remain a partial andincomplete science for so much of the informationavailable for the study of modern ecosystems is simshyply not preserved in ancient ones The animalsthemselves are all dead and their soft parts havegone the original physics and chemistry of the envishyronment is not directly observable and can onlybe inferred from such secondary evidence as is


available the shells may have been transported avayfrOlll their original enviromnents by currents andthe fossil assemblages that are found nlaY well bemixed or incomplete post-depositional diageneticprocesses may have altered the evidence still fllrtherDespite this palaeoecology remains a valid if partialscience Much is now known about the postshymortem history of organic remains (taphonomyChapter 12) of which an additional dimensioninvolves burial processes (biostratinomy) Thishelps to disentangle the various factors responsiblefor deposition of a particular fossil assemblage sothat assemblages preserved in situ which can yieldvaluable palaeoecological information can be disshytinguished from assemblages that have been transshyported

Biostratinorny or preservation history has bothpre-burial and post-burial clements The tannerinclude transportation physical chemical or biologshyical damage to the shell and the attaclullent of epishyfauna Post-burial processes may involvedisturbance by burrowers and sediment eaters (bioshyturbation) current reworking solution and otherdiagenetic preservation changes

Modern environments and vertical distribution ofanimals

Figure 14 shows the main environments within theEarths oceans at the present day and the nomenshyclature for the distribution of marine animals withinthe oceans

Modern marine environments are graded accordshyingly to depth The littoral environments of theshore grade into the subtidal shelf and at the edgeof the shelf the continental slope goes down todepth this is the bathyal zone Deloyv this lie theflat abyssal plains and the hadal zones of the deepshyocean trenches There is often a pronounced zonashytion oflife forms in depth zones more or less parallelwith the shore In addition there is a generaldecrease in abundance (number of individuals) butnot necessarily diversity (number of species) ondescent into deeper water from the edge of the shelfThe faunas of the abyssal and hacial regions wereoriginally derived tiom those of shallow waters butarc highly adapted for catching the limited foodavailable at great depths These regions 1re howshyever impoverished relative to the shallov-vvaterregIOns

Animals and plants that live on the sea floor arcbenthic those that drift passively or svim feebly inthe water column are planktic (= planktonic)since they arc the plankton Nekton (nektic ornektonic [lUna) on the other hand comprises activeswimmers Neritic animals belong to the shallowvvaters ncar land and include demersal clementsvhich live above the continental shelves and feedon benthic animals thereon Pelagic or oceanicfaunas inhabit the surpound1Cc waters or middle depths ofthe open oceans bathypelagic and the usuallybenthic abyssal and hadal organisms inhabit thegreat depths

5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC

Figure 74 Modern marine environments A Band C in the inset refer to supralittoral littoral and sublittoral environments (Basedon a drawing in laporte 1968)

Only the shelf and slope environments are norshymally preserved in the geological record the trenchsediments rardy so The abyssal plains are underlainby basaltic rock formed at the mid-oceanic ridgesand slowly moving away from them to becomefmally consumed at the subduction zones lyingbelow the oceanic trenches it moves as rigid platesThe ocean basins arc very young geologically theoldest sediments known therein being of Triassicage These are now approaching a subduction zoneand arc soon to be consllIned without trace Hencethere are very few indications of abyssal sedimentnow uplifted and on the continents

What is preserved in the geological record istherefore only a fraction albeit the most populouspart of the biotic realm of ancient times The sedishyments of the continental shelf include those of thelittoral lagoonal shallow subtidal rnedian and outershelf realms Generally sediments become finertowards the edges of the shelf the muddier regionslying of1shore There may be reefs close to the shoreor where there is a pronounced break in slope

Horizontal distribution of marine animalsThe main controls affecting the horizontal distribushytion of recent and f()ssil animals are temperature thenature of the substrate salinity and water turbushylencefhe large-scale distribution of animals in theoceans is largely a function of temperature whereasthe other factors generally operate on a more localscale Tropical shelf regions carry the most diversefaunas and in these the species are very nUlnerousbut the number of individuals of anyone species isrelatively low In temperate through boreal regionsthe species diversity is less though the number ofindividuals per species can be very large

Salinity in the sea is of the order of 35 parts perthousand Most marine animals are stenohalineie confined to waters of near-normal salinity Afew are euryhaline ie very tolerant of reducedsalinity The brackish water environment is physioshylogically difficult and poundnmas living in brackishwaters arc normally composed of very few speciesespecially bivalves and gastropods belonging to speshycialized and often long-ranged genera These samegenera can be found in sedimentary rocks as old asthe Jurassic and their occurrence in particular sedishyments which lack normal marine fossils is a valuablepointer to reduced salinity in the environment inwhich they lived


Water turbulence may exercise a substantJal conshytrol over distribution and the characters offaunas inhigh- and low-energy environments are otten verydisparate Robust thick-shelled and rounded speciesarc normally adapted for high-enerY conditionswhereas thin-shelled and fragile f(wms point to amuch quieter water environment and it may bepossible to infer much about relative turbulence in afossil environment merely from the type of shellsthat occur

MODERN AND ANCIENT COMMUNITIESIn shallow cold-temperature seas marine mverteshybrates are normally found in recurrent ecologicalcomrnunities or associations which are usually subshystrate related In these a particular set of speciesare usually found together since they have the samehabitat preferences Within these communities theanimals either do not compete directly beingadapted to microniches within the same habitat orhave a stable predator-prey relationship

Community structure is normally well defined incold-temperature areas but in warmer seas wherediversity is higher it is generally less clear

Petersen (1918) working on the faunas of theKattegat first studied and defined some of these natshyurally occurring communities I Ie also recognizedtwo categories of bottom-dwelling animals infaushynal (buried and living within the sediment) andepifaunal (living on the sea floor or on rocks orseaweed) It was soon found that parallel communishyties occur with the same genera but not the samespecies on the opposite sides of the Atlantic Sincethis pioneer work a whole science of communityecology has grown up having its counterpart inpalaeoecology Much effort has been expended intrying to understand the composition of fossilcommunities the habits of the animals composingthem community evolution through time and aspoundlr as possible the controls acting upon them (egThorson 1957 1971) This is perhaps the mostactive field of palaeoecology at present as a host ofrecent original works testifIes (eg Craig 1954Ziegler ct al 1968 Doucot 1975 1981 Scott andWest 1976 McKerrow 1978 Skinner et al 1981Dodd and Stanton 1990 Bosence and Allison1995 Brenchley and Harper 1997)

As FUrsich (1977) makes it clear however mostfossil assemblages lack soft-bodied animals Wherepossible trace fossils can be used to compensate for


this but they arc no real substitute Hence assemshyblages associations and even palaeocommuniticsmust not be considered as directly equivalent to thesea-floor communities of the present day Usingbiostratinornic and scdimcntological data thedegree of distortion trom the original communitycan in some cases be estimated

FEEDiNG RELATIONSHIPS AND COMMUNITIES

All Illodern animals feed on plants other animalsorganic detritus or degradation products The tinyplants of the plankton arc thc prhnary producers(autotrophs) as are seaweeds Small planktic anishymals arc the primary consumers (herbivores anddetritus eaters) there are secondary (carnivorcs)and tertiary consumers (top carnivores) in turnEach animal species is therefore part of a food webof trophic (ic feeding) relationships wherein thereare a number of trophic levels In palaeoecology itis rarely possible to draw up a realistic f()od web(though this is one of the more important aspects ofmodern ecology) but most fossil animals can usuallybe assigned to their correct feeding type and so thetrophic level may be estimated reasonably

Of primary consumers the following types areimportant

fllterers or suspension feeders vvhich are intmnalor epiplusmnclUnal animals sucking in suspended organicmaterial fro111 the waterepifnmal collectors or detritus fceders whichsweep up organic m~lterial poundi-0111 the sea floorsome infaunal bivalves and wornlS are also collecshytorssvvallowers or deposit feeders vvhich are intumalanimals unselectively scooping up mud rich inorganic material

Secondary and tertiary consumers the carnivores mayprey on any of these but it is the comrnunities of theprimary trophic level that are most commonly preshyserved because of their sheer number of individuals

In many living communities most of the bioshymass is actually contributed by very few taxa usushyally not more than five (the trophic nucleus) butthere may be representatives of a number of otherspecies in small numbers In this system competitionbetween the species concerned seems to be minishymized It is thus mutually beneficial since the dittershycnt taxa are exploiting different resources vvithin the

environment Living commtmities are therefore genshyerally well balanced the number of species and indishyviduals of particular species being controlled by thenature and availability offood resources Fossil assemshyblages may be tested according to this concept If theyare unbalanced then either (1) there may have beensoft-bodied unprescrvable organisms which originallycompleted the balance or (2) the assemblage has beenmixed through transportation and thus does notreflect the true original community

FAUNAL PROVINCES

Marine zoogeography (Ekman 1953 Briggs 1974Hallam 1996) is primarily concerned with theglobal distribution of marine faunas and vvith thedefinition of faunal provinces These are largegeographical regions of the sea (and most particushylarly the continental shelves) vllithin which the faushynas at the specific generic and sometimes familiallevel have a distinct identity In faunal provincesmany of the animals are endemic ie not plusmncmndoutside a particular province Such provinces areoften scparated from neighbouring provinces byplusmn~lir1y sharp boundaries though in other cases theboundaries may be more gradational

Figure 15 shows the main zoogeographicalregions of the present continental shelves as definedby Briggs (1974)

Tropical shelf warm temperate cold temperateand polar regions can be distinguished whose lirnitsare controlled by latitude but also by the spread ofymiddotvarrncr or colder water through major marine curshyrents T wpical shelf faunas occur in four separateprovinces Of these the large 1nelo-West Pacificprovince extending from southern Afi-ica to easternAustralia is the richest and most diverse and hasbeen a m~or centre of dispersal throughout theTertiary Smaller and generally poorer provinces oftropical faunas arc found in the East Pacific WestAtlantic and (least diverse of all) East Atlantic Theseare separated both by land barriers (eg the PanamaIsthmus) and by regions of cooler water (eg Aherethe cold Hmnboldt Current sweeping up the vestshyern side of South America restricts the tropical faunato vvithin a fe degrees south of the equator)

The shelf faunas of cooler regions of the vvorldare likewise restricted by temperature and againvvann or cold currents exercise a strong control oftheir distribution Some zoogeographic islands canbe isolated by regions of warmer or cooler water


- -

- Key

(())) tropical shelf

~ warm temperate

P-~= cold temperate

bull polar

0-----~ warm currents

-+- cold currents

Figure 15 Distribution of modern marine shelf-living animals in faunal provinces using Winkels Tripe projection (Based on adrawing in Briggs 1974)

Figure 16 Generalized section through a reef (algal or coral)

Modern and ancient reefsThroughout geological time animals have not onlybecome adapted to particular environments but alsothemselves created new habitats and enVirOl1lTlentsWithin these there has been scope for almost unlimshyited ecological differentiation

Perhaps the most striking examples of such bioshygenic environments are the reefs of the past andpresent Reefs (Fig 16) are massive accumulationsof limestone built up by lime-secreting algae and byvarious kinds of invertebrates

Through the activities ofthese frame-builders greatmounds may be built up to sea level with cavesand channels within them providing a residence for

For example the tip of Florida ca rries a tropical shelf[luna isolated to the northeast and northwest bycooler water areas but though this is part of theWest Atlantic tropical shelt- province it has been isoshylated for some time and therefore its [luna hasdiverged somewhat trorn that of the Caribbeanshelf Likewise some oceanic islands (eg theGalapagos) may be considered as part of a generalzoogeographic region or province but as theirshelves have been initially colonized by chancemigrants they may have very many endemic eleshyments vhich have evolved in isolation How manyof these endemics there arc may depend largely onhow long the islands have been isolated

The development of todays faunal provinces hasbeen charted throughout most of the Tertiary Atpresent Mesozoic and Palaeozoic provinces are likeshywise being documented (Middlerniss et al 971Hallam 1973 Hughes 1975 Gray and Boucot1979 McKerrow and Scotese 19(0) When used inconjunction with palaeocontinental maps it may bepossible to sec how the distribution pattern ofancient faunas related to the position ofancient conshytinental masses and their shelves Sometimes palaeoshyzoogeographical and geological evidence may havea bearing upon palaeotemperatures and even allowsome inference to be made regarding ancient oceancurrent systerns

BASIN SLOPE RIM lAGOON OR SHFLF


innumerable kinds of animals all ecologically differshyentiated for their particular niches

In the barrier and patch reef of the tropical seasof today which grmv up to the surface the warmoA)Tgen-rich turbulent waters allow rapid calciummetabolism and hence cominuollS gn)vth Theprincipal frame-builders are algae and corals butthere are many other kinds of invertebrates in thereef community sponges bryozoans and molluscsnnongst others SOllIe of these add in minor yvays tothe reef framework others break it down by boringand gr3zing The growth of the reef to sea levelcontinually keeps pace vvith subsidence but it is alsobeing continually eroded In a typical coral reefcomplex the reef itself is a hard core of celnentedalgal and coral skeletons poundIcing seawards and as thereef subsides it grows outwards over a forerccf slopeof tumbled boulders broken from the reef fi-ontBehind it is a lagoon with a coral sand sediment andtidal flats along the shore colonized by cyanobacteria(blue-greens) Green algae are commonest in theback-reefpoundtcies red algae are the main lirne senctersof the reef itself

Large reefs such as the above are knovvn as bioshyherms they form discrete mounds rising (iom thesea floor Biostromes on the other hand are flatlaminar communities of reef-type an imals and barelyrise above the sea floor

Throughout geological history there have beenvarious kinds of reef cormnunities which havearisen flourished and become extinct In all of thesethe frame-builders have included algae but theinvertebrate frame-builders have been of diHcrentkinds the present corals are only the most recent ina series of reef-building animals (Newell 1972)

The oldest known reef He over 2000 Ma oldmade up entirely of sediment-trapping and possiblylime-secreting cyanobacteria the prokaryotic stroshymatolites Some of these reef reached considerabledimensions One is reported from the Great SlaveLake region in Canada as being over 450 rn thickand separating a shallow-water carbonate platformfrom a deep-water turbidite-filled basin There areno preserved metazoans in these reefs however andtheir ecological structure Inay have been very simshyple

With the rise of frame-building metazoans in theLower Cambrian a new kind of reef communitymade its appearance Stromatolitic reefs wereinvaded by the sponge-like archaeocyathids grow-

ing in clumps and thickets on the reef surfaceWhen these earliest of reef invertebrates becameextinct in late Middle Cambrian time there vere no1110re reef anin131s until some 6() Ma later the onlyreefs VelT stromatolitic In 1vliddk Ordovician timethese algae were joined by corals and stromatoshyporoids (lime-secreting sponges Chapter 4) as wellas by red algae vlhich together formed a reef envishyronment attracting a host of other invertebratesll1c1uding brachiopods and trilobites ror unknownreasons this type of reef complex did not continuebeyond late I)evonian time 1he reefs that arose inthe Carboniferous were THainly algal stromatoshyporoids and corals no longer playing such an imporshytant part in their construction

The same kind of reef continued into thePermian and many of these fringed the shrinkingin1Jnd seas of thJt time They rose at the edge ofdeeper basins in which the water periodicallybecame more saline as it evaporated there was likeshywise evaporation in giant salt pans behind the reef aswater drawn through the reef dried out in thelagoons behind In the Permian reds of Texas andnorthern England which are very large the reeffront rose as a vertical vall of laminated algal sheetsturning over at the reef crest where it reached sealevel (Fig 17)

The upper sUli~lce vas intensely colonized bystromatolites which died out towards the lagoonalback-reef f1cies This kind of reef in general morshyphology therefore does not closely approximate thestandard pattern of Fig 16 When the Permian shelfseas had dried out completely the Pennian reefshycomplex type vanished and there were no morcreefS until the slOv beginnings of the coral-algal reefsystem that arose in the late Triassic Coral reef)

reef-flat

100 m

scale Ivortlcal and homolltall

Figure 17 Crest of a Permian algal reef (Redrawn from Smith1981)

have expanded and flourished since then other thanduring a catastrophic period in the early Cretaceousitom which there are no reefs known (though coralsmust have been living somewhere at that time)When the corals recovered they were joined inmany places by the peculiar rudistid bivalves alsoreef fonners which at one period almost supplantedcorals as the dOlninant reef frame-builders Yet thesetoo died out in the late Cretaceous leaving coralsthe undispu ted and domina nt reef-building inverteshybrates

There has been some decline in the spread ofcoral reefs and in the number of coral genera sincethe beginning of the Tertiary They arc now conshyfined to the Indo-Pacific region and on a smallerscale to the West Atlantic This decline may still becontinuing though the reeflt were not significantlyaffected by the Pleistocene glaciation The tllture oforld reef communities the most complex of alll11arine ecosystems rernains to be seen

Functional morphology growth and formThe functions of particular organs in fossils cannotbe established by many of the nrethods available tozoologists but it is still possible to go some waytowards explaining how particular organs workedwhen the animal that bore them was alive Suchfunctional interpretation is however limited and inmany ways it is hard to go beyond a certain pointeven when the function of a particular organ isknown (section 113)

Palaeoltologists arc otten presented either withorgans whose function is not clear and which haveno real counterparts in living animals or with fC1ssiisof bizarre appearance which arc so modified fromthe normal type for the taxon that they testif~l to

extreme adaptations Sorne attempts can be madetowards interpreting these morphologies in terms ofadaptation and mode oflitC which in tum may leadto a clearer understanding of evolutionary processesIf these problems are to be tackled then a coherentmethodological scheme is needed One particularsystem of approach the paradigm nlethod ofRudwick (1961) has been much discussed but itlies largely outside the scope of this work andso only some examples of its application arementioned

Tvo related aspects of palaeozoology which canbe deduced from fossilized renrains alone are growthand t(1nn Following the classic work of dArcy


Thompson (1917) it has been understood that theconfounation of the parts of any organism is theresult of interacting forces dictated by physicomathshyematical laws which have operated throughgrowth The central issue here (Thonras and Reif1993) is the balance perceived between aCCIdents ofhistory and the prescription of physical laws ascauses of organic design

Different marine invertebrate skeletons may befunctionally convergent in the way they growand the sanre kinds of growth patterns turn upfrequently in representatives of many phyla Thisis because there arc relatively few ways in whichan animal can grow and yet can produce a hardcovering Invertebrate skeletons by contrast withthose of vertebrates are generally external and thisnarrows down the spectrum of growth possibilitiesstill further Some of these types of skeletons are asfollows

External shells growing at the edges only byaccretion of new material along a particular marshyginal zone of growth Very often such growthresults in a logarithmic spiral shell as in brachioshypods cephalopods and in coralla of certain simplecoralsExternal skeletons of plates - di~iunct contiguousor overlapping - normally secreted along a singlezone which may be but is not always marginal Agood example is the echinoderm skeleton inwhich the plates once formed are permanentlylocked into place though they may thereaftergrow individually by accretion of material in conshycentric zonesExternal skeletons all formed at the one tinieThe arthropod exoskeleton is most typicalGrowth here is ditflcult for the skeleton has to beperiodically moulted a process known as ecdyshysis When the old exoskeleton is cast the arthroshypod takes up water or air and swells to the nextlarger size and the new cuticle which underliesthe old one then hardens Growth is thus rapidand episodic and is only possible during moultingThe disadvantage of this system is the vulnerabilshyity to damage and predation during moulting

Essentially any kind of skeleton internal orexternal is highly constrained by geometric rulesgrowth processes and the properties of materialsThis suggests that given enough time and an


extremely large number of evolutionary expenshyments the discovery by orgmisIlls of gooddesigns - those that are viable and can be conshystructed with available materials - vas inevitable andin principle predictable the recurring designs weobserve arc attractors orderly and stable configurashytions of matter that must necessarily emerge in thecourse of evolution (Thomas and Reif 1993)

In point of ElCt the potential available has beenvery well exploited by living creatures though speshycific constraints seldom allow the production ofideal organisms Nature works as a tinkerer ratherthan as an engineer Oacob 1977 see also Chapter 2)- a point to be borne in mind in considering alllivshying and fossil organisms

Stratigraphy

Sedimentary rocks have been built up by layer uponlayer of sediment which sornetimes has been muchthe same for long periods of time but at other timeshas changed its character rapidly The individuallayers vithin sedimentary rocks arc separated bybedding planes These bedding planes are time horishyzons and the history of a rock sequence is reflectedin its layering Each layer in the rock sequence musthave been laid down on a pre-existing layer so thatthe oldest rocks arc at the bottom of an exposedsequence the youngest at the top unless the successhysion has been tectonically inverted This is the prinshyciple of superposition recognized as long ago as1669 by the Danish scientist Nicolaus Stecnscn(Steno)

Stratigraphy is concerned with the study of stratishyfIed rocks their classification into ordered units andtheir historical interpretation It bears not only uponpast geological events but also upon the history oflife and is perhaps the most basic part of all geology(Harland and Anllstrong 1990 Benton 1995)

Much of stratigraphy is concerned with chronolshyogy the geological record has to be divided up intotime periods which are standardized as far as possishyble all over the world One of the primary aims ofstratigraphy has been to produce an accuratechronology in which not only the order of eventsbut also their dates arc known Stratigraphical classishyfication is basic to all of this

There are three principal categories of stratishygraphical classification lithostratigraphy bio-

stratigraphy and chronostratigraphy all of whicharc ways of ordering rock strata into meaningfulunits (Hedberg 1976 Holland et al 1978)

LithostratigraphyLithostratigraphy is concerned vvith the erection ofunits based upon the characters of the rocks and difshyferentiated on types of rock eg siltstone limestoneor clay It is useful in local areas and essential ingeological mapping but there is ahvays the dangerthat even in a small area rock units cut across timeplanes For instance if a shoreline has been advancshying in one direction a par6cular suite of sedimentsprobably of the same general kind li]] be left in itswake Though this bed will appear in the rockrecord as ] single uniform layer it will not all havebeen deposited at the one time since it cuts acrosstime planes it is said to be diachronous Suchdiachronism is common in the geological recordFurthermore Blany suites of sediments arc laterallyimpersistent different sedimentary Ell~ies rnay haveexisted at the same time within a small spacc- asandstone layer for instance passing into a shalesome distance away Lithostratigraphy is thus only ofreal value within a relatively small region

The divisions erected in lithostratigraphy arcarranged in a hierarchial system group formashytion luember and bed A bed is a distinct layer ina rock sequence A member is a group of bedsunited by certain common characters A formationis a group of members again united by characterswith features in common It is the primary unit oflithostratigraphy and is rnost usetll1 in geologicalmapping Hence it is formations that arc normallyrepresented by diHcrent colours on geological mapsand cross-sections and a formation is normallydefined tor its mapping applications Finally a groupranks above a formation it is composed of two ormore tormations and is often used for simplifyingstratigraphy on a small-scale map

BiostratigraphyJ11 biostratigraphy the fossil contents of the beds arcused in interpreting the historical sequence It isbased upon the principle of the irreversibility ofevolution This means that at anyone moment inthe Earths history there was living a unique andspecial assemblage of animals characteristic of thatperiod and of no other As time went on these werereplaced by others each successive fossil assemblage

is a pale reflection of the life at the time that theenclosing sediments were deposited Thus duringthe early Palaeozoic trilobites and brachiopods werethe n10st con1mon fossils By the Mesozoic tbe mostabundant preservable invertebrates were theammonites they too became extinct and snails andbivalves arc the commonest relics of Cenozoic timeThis is how it appears on a broad scale Howeverwhen the time ranges of individual f()ssil species arcexamined it is evident that some of tbese lasted fc)[only a traction of geological time characterizingvery precisely a particular brief historical period

In any local area once the sequence of fossil flUshynas has been precisely established through assiduouscollection and docmnentation from exposed secshytions this known succession can be used for correlashytion with other areas Certain fossil species havebeen found to be particularly good stratigraphicalmarkers They characterize short sections of thegeological succession known as zones To take anexample ammonites are particularly good zone f()sshysils fc)r Mesozoic stratigraphy The Jurassic periodlasted some 55 Ma and in the standard British sucshycession there arc over 60 ammonite zones by whichit is subdivided so the zones are defined historicalperiods which have m average duration oflcss thana million years each

The practical problems in biostratigraphy arehowever very complex and some parts of the geoshylogical succession are much more closely zoned thanothers The main problems are as follows

I Many kinds of fossils especially those of bottOITlshydwelling invertebrates are flcies controlled Theylived in particular environments only eg liIneshymud sea floor reet~ sand or silty sea floor Theywere often highly adapted fc)r particular condishytions of temperature salinity or substrate and arcnot found preserved outside this environmentThis means that they can only be used for correshylating particular environments and thus arc notun iversaHy applicable

2 Some kinds of fossils are very long-ranged Theirrates of evolutionary change were very slowThey can only be used in a broad and generalsense for long-period correlation and arc of verylittle use for establishing close subdivisions

3 Good zone fossils such as the graptolites are delishycate and only preserved in quiet environmentsbeing destroyed in more turbulent conditiolls


4 Since fossil species could migrate following theirown environment through time there is always apossibility of diachronous faunas The zone asdefined in one area may not therefore be exactlytime-equivalent to that in another region

In the example of a graptolite therefore for thereasons outlined in (3) and (4) the total range orbiozone of a species is not likely to be preserved inany Olle area and it is therefore hard to draw idealisochronous boundaries or time lines

Ideally zone f()ssils should have a particular comshybination of characters to make them fully suitablefor biostratigraphy These would be

a wide horizontal distribution preferably intershycontinentaLa short vertical range so that they could be used todefine a very precise part of the geological colshylllllnenough morphological characters to enable themto be identified and distinguished easilystrong hard shells to enable them to be comshymonly preservedindependence of facies as would be expectedfrom a free-swimming animal

All of these conditions are seldom fillfilled in fosshysils used for zonation perhaps the neritic ammonitescome closest to it and it is not surprising that theprinciples of really precise stratigraphical correlationwere first worked out fully with these fossilsnotably by the German palaeontologist A Oppel inthe 1850s

It was Oppel too who first recognized that thereare various ways of using fossils in stratigraphywhich partially circumvent the difficulties nlenshytioned and hence different types of biozones Thereare four main kinds of biozones generally used(Hedberg 1976) Assemblage zones are beds orgroups of beds with a natural assemblage of fossilsThey may be based on all the fossils preservedtherein or on only certain kinds They arc usuallyvery much environmentally controlled and thereshyfore of usc only in local correlation Range zonesare perhaps of Inore general application A rangezone usually represents the total range of a partiCllshylady useful selected element in the fauna One maytherefore refer to the Psiloccras planorbis zone basedupon the eponyInous ammonite that defines the


aThese terms are in most common use

Table 11 Conventional hierarchical correlation belweenchronostratigraphical and geochronological units

mere is as before expansion and diversification folshylowed by extinction Several such biomeres havebeen detlned in the intensively studied UpperCambrian of North America The pattern is invarishyably similar and could probably be discerned inother parts of the geological column as well

ChronostratigraphyChronostratigraphy is more tlr reaching than eitherbio- or lithostratigraphy but has its roots in both ofthem Its purpose is to organize the sequence ofrocks on a global scale into chronostratigraphicalunits so that all local as well as vorldvide eventscan be related to a single standard scale l-lcnce it isconcerned with the age of strata and their time relashytions To do this a hierarchical classification of tirneshyequivalent units must be employed Theconventional hierarchical system used is as shOvn inTable 11

AeonEraa

Perioda

Epocho

AgeChron

Geochronological units

EonothemErathemSystemo

Seriesa

StageChronozone

Chronostratigraphical units

Chronostratigraphical units relate quite simply to

geochronological units thus the rocks of theCambrian System were all deposited during theCambrian Period Most of these terms arc sclfshyexplanatory but it should be recognized that theyare all at least in theory worldwide in extent

The Psiloceras planorbis chronozone is a time unitequivalent to the time in which the said ammonitewas in existence even if it was confIned to certainparts of the world only It is hard indeed howeverto be able to delimit chronozones accurately sincemost fossils were confined to certain gcographicalregions or provinces as arc most of the animals livshying today There arc relatively few well-establishedcllronozoncs or world instants as they have beencalled and so chronmone though it has a realmcamng is not a term applicable to most practical

lowest zone of the European Jurassic above whichis the Schlotheimia imgulata zone Each range zone isalways named after a particular species which occurswithin it Where there afe a number of zonally useshyful species or where the ranges of individual speciesarc long a more precise time definition may begiven by the usc of overlapping stratigraphicalranges Such zones are therefore called concurrentrange zones Acnle or peak zones are usefullocally An acme zone is a body of strata in whichthe maximum abundance of a particular species isfound though not its total range Such acme zonesmay be narrow but are often useful as marker horishyzons in geological mapping finally an intervalzone is an interval between two distinct biostratishygraphical horizons It l11ay not have any distinctivefossils or indeed any fossils at all being simply aconvenient way of referring to a group of stratabracketed betveen two named biostratigraphicallydefined zones

Biostratigraphical units unlike litho- andchronostratigraphical units are not hierarchiallyarranged apart frOln in the case of subzones whicharc local divisions where a zone can be dividedmore fInely in a particular region than elsewhere

A difterent kind of stratigraphic concept the bioshyntere (Palmer 1965 19R4) was defined as aregional biostratigraphic unit bounded by abruptnon-evolutionary changes m the dominant clementsof a single phylum These changes are not necessarshyily rclated to physical discontinuities in the sedimenshytary record and they may be diachronous Thebiomere concept has proved rnost useful in studiesof late Cambrian trilobite faunas where a repeatedpattern of events is evident from the fossil record Ineach biomerc the shelf sediments contain an initialf~lUna of low diversity and short stratigraphical range(one or tTO species only) I Iowever later faunaswithin the biomere become much more diversitledand of longer stratigraphic range and suggest by thisstage sound adaptive plans and the zenith of thetrilobite fauna At the top of the biomere there isoften a rather specialized fauna of short-lived triloshybites then all the groups become extinct abruptly

The succeeding biomere begins in the same wayas its predecessor often with trilobites of similarappearance to those at the base of the first one Thc)may have rnigratcd in ii-om a stock of more slowlyevolving trilobites in an outlying possibly deepershywater area The later development of the nev bio-

stratigraphy A stage on the other hand is a groupof successive zones having great practical usc espeshycially since it is normally the basic working timeunit of chronostratigraphy the narrowest that canactually be used on a regional scale

It is usually at the stage level that rocks of widelydifferent poundlcies can be correlated As an examplethere are some ditticulties in making precise zonalcorrelations between Ordovician trilobite-brachioshypod tnmas and time-equivalent faunas with graptoshylites Graptolites arc rarely preserved in the siltstonesand limestones favoured by the shelly fossils and thelatter being benthic could not inhabit the stagnantmuds in which the graptolites were best preservedIn some areas of course the faunas do alternate invertical sequence since the sites of deposition ofthese two tCies fluctuated with oscillating shoreshylines but though precise zone-to-zone correlationsare possible at some levels it is tl)Und in practice thatOrdovician graptolite zones correlate best withstages dcflned on shelly fossils

Fossils give a relative chronology which can beused as the primary basis of chronostratigraphyNevertheless it is otten hard to correlate preciselybeds of equivalent age 111 widely separated areasThe fossil sequences though well documented withanyone area may contain very few e1enlents incommon if indeed any at all since they belong todiflerent Ewnal provinces which are hard to correshylate Sometinles however the boundaries of suchprovinces may have oscillated to and tJ-o There maytherefore appear elements of adjacent faunal provshymces in vertical succession thus [1cilitating stratishygraphical correlation At most stratigraphical horizonsthere are usually some ubiquitous worldwide fl)ssilsso that intercontinental correlation is not impossible

In chronostratigraphy the relative sequence givenby the f()ssils is supplemented and enhanced byabsolute dates which can be affixed at certain pointswherever appropriate rocks occur These are usuallylavas bracketed betveen fossiliferous sediments andtheir occurrence is not too common It is mostunlikely therefore that radiometric dating willsupersede palaeontological correlation the two arcentirely complementary and the great success ofchronostratigraphy in spite of its limitations owesmuch to both The use of automatic data-processingand retrieval systems is growing and may (Hughes1989) compensate for some of the constraints inpresent stratigraphical practice

Bibliography 23

Books treatises and symposia

Agel DV (1963) Prilciples of Palaeoerol(~y McGrawshyHill New York (Useful basic text)

Barrington EJW (1967) lt11Jertebrate Strtcture andFl1nction Nelson London (Invaluable zoology text)

Benton M] (1995) The Fossil Record 2 Chapman ampHall London (Invaluable summary of stratigraphicaldistribution of all known fossil genera)

Boardman RS Cheetham AI-l and Powell A] (cds)(1987) Fosiil Invertebrates Blackwell Oxford(Exceptionally Llsdid multi-author text)

Bosenee DW] and Allison PA (1995) (cds) fClrinepabeoC11vironmental analysis from fi)ssils GeologicalSociety ofLondon Spccial Publication No 83 (12 uscshyful papers)

Boucot A (1975) Evolution dnd Extinction Rate ControlsElsevier Amsterdam (Advanced text mainly dealingwith brachiopod distribution)

I3oucot A] (1981) Principles of Benthic MarinePalaeoecology Academic Press New York (Valuable ifidiosyncratic)

Brenchlcy P and I Iarper DAT (1997) EcosystemsEcology and Elo111tion Chapman amp I all London(New vigorous and readable text)

Briggs DEG and Crowther D (1990) Pdlacobiology aSywl1esis Blackwell Oxford 583 pp (The best andmost Llseful palaeontological compendium of all)

Briggs JC (1974) lVaril1e Zoogeography McGraw-HillNew York (Delimitation of faunal provinces)

Bruton DL and lIarpcr I)AT (1990) Microshycomputers m palaeontology Contributions of thefYalaeontological JlhtSfltl11 Oslo 3701-105 (8 papers)

Cowen R 1994 History of Liti~ 2nd edn BlackwellOxford (Eminently readable)

Dodd JR and Stanton R] (1990) PalaeoewlogyCoucepts wd Applications 2nd edn Wiley New York502 pp (Interesting approach)

Ekman S (1953) ZOoeography of the Sed Sidgwick andJackson London (An older but still usdid text onmarine life zones and taunal provinces)

Eldredge N and Cracraft J (1980) Phylogenetic Patternsand the Evolntionary Process Columbia University PressNew York (Explains cladistic methods)

Fairbridge RW and Jablonski D (eds) (1979) TheEncyclopedia of Earth Sciences Vol VII The Encyclopediaof Paleontology Dowden Hutchinson and RossStroudsberg Penn (Invaluable reference)

Goldring R (1991) Fossils in the Field InformationPotential and andlysis Longt11an Harlow (Howpalaeontological information is gathered in the field)

Gould SJ (1990) I1onderfiti Life the BI1~ess Slwle and the


nature Cf histOly Hutchinson Radius London(Comments on taxonomy)

Gray J and BOllcot A (eds) (1979) Historical Bio~eoshy

graphy Plate Tectonics af( the Chal1ginc~ Hillironlien I

Oregon State University Press Corvallis Ore (Severalpapers on faunal provinces)

Hallam A (1973) Atlas of Palaeobi(~Reography ElsevierAmsterdam (48 original papers on distribution of fossilfaunas)

Hallam A (1990) 1 n Outline or Phanerozoic BiocographyOxford University Press Oxford

I brIand wn (cd) (1976) The Possil Record - aSymposium with Documentation Geological Society ofLondon London (Contains time-range diagrams of alltl)ssil orders and charts showing diversity fluctuationsthrough time)

Harland WB and Armstrong RL (1990) J1 Geoh~gi((ll

Time Scale Cambridge University Press Cambridge253 pp (Essential and up~to-date)

Hedberg HD (1976) International Srratigraphir GuideWiley New York (Official guide to stratigrapillcalprocedllre)

Hedgpeth J W and Ladd ]S (1957) Trearise on Marincbcology and P(lacoe(OIlt~y Vols 1 and 2 Memoirs of theGeological Society of America No 67 GeologicalSociety of America Lawrence Kan (Standard textwith papers and annotated bibliography on ecology ofaJlliving and fossil phyla)

HennigW (1966) Phylofcnetic Systematics University ofIllinois Press Urbana Ill (Original chdisrn secondedition published in 1979)

Hughes NF (cd) (1975) Otg(misms and ContillcnlsThrough Tilllc Special Papers in Palaeontology No 17Academic Press London (23 original papers on distrishybution of fJunds many charted on global maps)

I Jughes NF (1989) Possils as Injonnation New Rcwrdinxand Srratal Correlation Tedi1liq~tes Cambridge UniversityPress Cambridge 144pp

Joysey KA and Friday AE (1982) Prohlems ltf Pl1yloshycnctic Reconstruction Systematics Association SpecialVolume No 21 Academic Press New York (11papers)

Laporte L (196~) Ancient Elwironments Prentice-I TallEnglcvood Cliffs NJ

McKerrow WS (1978) The Ecology (d Fossils])uckworth London (Community reconstructions)

McKerrow S and Scotese CR (eds) (1990) Palaeozoicpalaeogeography and biogeography GeologicalSociety Memoir No 12 pp 1-240 (Many valuablepapers including Palaeozoic vorld maps)

Middlemiss FA Rawson PF and Newall G (cds)(1971) Faunal PYOIlIces in Space alld Time Seel HousePress LiverpooL (13 original papers on faunal distribushytion)

Moore RC Teichert C Robison RA and KaeslerRC (successive editors from 1953) Treatise 011

11I1crtebrate Paleontology Geological Society ofAmerican and the University Kansas Press LawrenceKarl (The standard reference work on invertebrate fosshysils - each phylull1 treated in separate volumes)

Murray J-W (ed) (1986) Atlas ~f Invertebrate lacr~lo5sils

Longman Harlow fi)r the Palaeontolotgt1cal Association(Excellent photographic coverage of main groups)

Paul CRC (1980) The Natural History of FossilsW cidenfeld and Nicolson London (Simple but intershyesting)

Pivcteau J (cd) (1952-1966) Trait de paleolltologieMasson Paris (The French Treatise slightly olderthan the American Treatise 011 Invertebrate Paleontologybut of very high quality)

Raup nM and Stanley SM (1978) Principles ofPale(mtoh~ifY 2nd ecin Freeman San Francisco(Excellent textbook emphasizing approaches and conshycepts but not morphological or stratigraphical details)

Ridley M (19K)) Evolution and Classification TheRlfomwtioll (~r Cladism Longman Harlow 201 pp(Clear treatment of different approaches to classificashytion)

Ryan P Harper DAT and Whalley ]S (1995) PALshyS T [her 5 manual and case histories Slatistice j)rpalaeontoh~lists 71 pp and disc Chapman amp HallLondon and Palaeontological Association

Schifir W (1972) Ecology and Palaeoecology oj A1arinebwironmcnts (translated edn) (cd GY Craig) Oliverand Boyd Edinburgh (Standard work on RecentNorth Sea environments with applications for palaeoshyec0106))

Schopf TJM (ed) (1972) Afodcls in PaleobiologyFreeman Cooper San Francisco (10 original papersmany significant)

Scott RH and West RR (cds) (1976) Structure andClassification of Palcocomnlunities Dcvdcn Hutchinsonand Ross Stroudsberg Penn (11 original papers)

Skinner BJ (ed) (1981) Palcontology and paleocnvironshyIncuts Readinlts fronT American Scientist Kaufmann LosAltos Calif (21 collected papers)

Smith AB (1994) Systematics alld the fossil recordDocUfncntillg elofurionary patterns Blackwell Oxford(Lucid explanation of cladistic methodology)

Sylvester-Bradley Pc (cd) (1956) The Species Concept inPalaCOnIOI(~ly Systematics Association London (Basicwork of several papers on palaeontological taxonomy)

Teichert C (1975) Tmltisc 011 Iuvcrtcbrate PaleontologyPart VvT (Suppl 1) Trace Fossils and ProblematicaGeological Society of America Lawrence Kan

Thompson d Arcy W (1917) 011 Growth and FormCambridge University Press Cambridge (individshyualistic classic work on physical laws determining

growth an abridged edition of this book was edited byJT Bonner in 1961 and also published by CambridgeUniversity Press)

Thorson G (1971) Lire in the Sea World UniversityLibrary London (Simple well illustnted text dealswith commLltlity structure)

Valentine JW (1973) Ellolutionary Palaeoecolo~y (~f theji[arine Biosphere Prentice-Hall Englewood Cliffs NJ(Valuable text on evolution and ecology)

Willmer P (1990) Inllertebrate Relationships CambridgeUniversity Press Cambridge 400 Pl (Modern veryreadable and up-to-date treatment)

Individual papers and other references

Craig GY (1954) The palaeoecology of the Top I-JosieShale (Lower Carboniferous) at a locality near KilsythQuarterly Journal of the Geological Society or London 110103-19 (Classic palaeoecological study)

Fortey RA and JdIeries R (I f)81) Phylogeny andsystematics - a compromise approach in Problems ofPhylogenetic Reconstruction (eds KA Joysey and AEFriday) Academic Press New York Pl 112~47

(Wh~re cladistics is and is not useful)Fiirsich FT (1177) Corallian (Upper Jurassic) marine

benthic associations from England and N orrnandyPalaeoutolopy 20 337--middot85 (Palaeoecol0oy mainly ofbivalve communities)

Gingerich PD 1110 Stratophenetics in Palaeobio~RY aSynthesis (eds DEG Briggs and PR Crowther)Blackwell Oxfcwd 437-42

Harper DAT (1989) Brachiopods from the UpperArdmillian succession (Ordollicllw) of the Ginau DistrictScotland Part 2 79middotmiddot-128 Palaeontographical SocietyMonographs (taxonomic procedure referred to in text)

Harper DAT and Ryan P (1990) Towards a statisticalsystem for palaeontologists Journal of the GelllogicalSociety of London 147 935-48 (Essential reading)

lemy J-L (1984) Analyse c1adistique et Trilobites unpoint de vue Lethaia 1761-6 (Use and hrnitations ofc1adism)

Holland CH Audley-Charles MG Bassett MG etal (1978) A guide to stratigraphic procedureGeological Sociery of London Special Report No 10Pl 1-43 (Invaluable modern rreatment)

Jacob F (1977) Evolution and tinkering Scietlce t 961161-~7

Bibliography 25

Kautfmann EG and Scott RW (1976) Basic conceptsof community ecology and palaeoecology in Structureaud Classificatioll of Palaeocommunities (cds R W Scottand Rl~ West) Dowden Hutchinson and RossStroudsberg Penn Pl 1-28

Lockley M (1983) A review of brachiopod dominatedpalaeocommunities trom the type OrdovicianPalaeontology 26 111-45 (Terminology for palaeoshycommunitv structure)

Moore J and Willmer P (1997) Convergent evolutionin invertebrates Riological Reviews 72 1-60

Newell ND (1972) The evolution of reefs ScientificAIlerican 226 54~65 (InfcJrInative short paper)

Palmer A R (1965) Biomere - a new kind of stratishygraphic unit JOllrnal of Palaeontology 39149-53

Palmer AR (1984) The biomere problem evolution ofan idea Journal of Paleotltology 39 149-53

Petersen (~CJ (1918) The sea bottom and its producshytion of fishfood Reports of the Danish BiologicalStation 25 1~62 (The first definitive summary of benshythic communities)

Pickerill R K and Brenchley P (1975) The applicationof the cOInIllunity concept in palaeontology JIaritimeScdilllerits 11 5-8 (Terminology and application)

Rudwick MJS (1961) The feeding mechanism of thePermian brachiopod Prorichthofnia Palaeontolt~RY 3450~71 (paradigm approach)

Smith DB (1981) The Magnesian Limestone (UpperPermian) reef complexes of north-east England inEllropean Relf A10dels (cd DF Toomey) Society ofEconomic Paleontologists and Mineralogists SpecialPublication No 30 Tulsa Oklahoma SEPM PI161-8

Thomas RDK and Reif W-E (1193) The skeletonspace a flnite set of organic designs Evolution 47341-60

Thorson G (1957) Bottom communities in Treatise onA1arille bcology alld Palaeoecology Vol 1 (eel JWHedgpeth) Memoirs of the Geological Society ofAmerica No 67 Geological Society of AmericaLawrence Kan Pl 461~534 (Standard work invalushyable well illustrated)

Ziegler AM Cocks LR M and Bambach RK(1968) The composition and structure of LowerSilurian marine communities Lethaia 1 1-27 (Thefirst major work on Lower Palaeozoic communitiesvery vell illustrated)

Evolution and the fossilrecord

Amongst all the sciences concerned with organicevolution it is only palaeontology that has theunique perspective of geological time It is the rockrecord alone that provides an historical perspectivefor the study of evolutionary events and this timedimension could never have corne from any othersource Accordingly the input of palaeontology to

evolution theory has been in understanding the hisshytory of life in interpreting patterns of evolution(eg adaptive radiations) and lines of descent andimportantly in assessing rates of evolution Now ithas to be admitted that the fossil record is incomshyplete and to interpret it can in some instances belike trying to rcad a diary with half the pagesmissing (Sheldon 19KK) Yet it still remains animmensely rich source of primary data and cangive if resotved finely enough a fair picture of evoshylutionary events that actually took place howeverlong ago

The student of palaeontology needs to have somebackground in biological evolutionary theory othershywise he will be in the position of the man standingby the roadside and watching the cars go past butwithout any idea of how their engines work to useBrouwers (1973) graphic simile for the fi)ssilrecord cannot give much information on the mechshyanism of evolutionary change this has to be proshyvided by genetics cytology molecular biology andpopulation dynamics building upon the originalconceptions of Charles Darwin Many years ago thefirst real multidisciplinary amalgam of data was pubshylished as EfJoution the i1odern SYlzthesis (Huxley1942) From this highly successful atternpt at weldshying together Illt~rmation trom various sources thenco-Darwinian synthesis takes its name - and this isa useful starting point But recent developments in

molecular biology arc transforrning and adding tothis synthesis and new views on the nature of thegene seem to be changing our whole conception ofhow organisms evolve

In the f()llowing text therefore I present firstly asimplified account of classic neo-Darwinian evolushytionary theory aimed particularly at students ofEarth science who may only have a limited backshyground in biology This includes some informationon the impact of neyv information from moleculargenetics all evolution theory This section is notintended to be comprehensive nor does it pretendto be a guide to all recent developments and disshycoveries Fuller treatments are readily available eJseshyvhe1e viz Simpson (1953) Maynard Smith (1lt)751982) Mayr (1963 1(76) Dawkins (1986)Dobzhansky ct a (1977) Gamlin and Vines (1987)Bonner (1988) Endler and l1cLellan (1988)Hoffrnann (1989) Carnpbel1 and Schopf (1994)Maynard Smith and Szathmary (1995) Futuyma(1996) Strickberger (1996) Ridley (1996) andothers listed in the bibliography while Valentine(1973) Hallam (1977) Stanley (1979) Cope andSkelton (1985) Levinton (1988) and Skelton (1993)arc more directly concerned with evolution andthe fossil record In the second part of this chapterthere is a more extended account of vhat the fossilrltcord can tell us about the nature of evolutionarychange

The theory ofevolution links together a multiplicityof biological phenomena and is underpinned by allthe evidence of the geological record It remains atheory not a proven [let tor the immense timescale

over which evolutionary changes have taken placedoes not permit their direct observation There ishowever no other theory which encompasses somuch and accords with the evidence of comparativeanatomy biochemistry and physiology of geneticsand cytolotY and of the relationships betweenorganisms perceived by taxonomy Whereas theevidence in some of these fields is circumstantialwhen brought together and interpreted it builds upto a theory of formidable consequence and asDobzhansky has said Nothing in biology makessense except in the light of evolution

The recent facile attempts to discredit evolutionby self-styled creation scientists have been so eloshyquently dispatched by Dott (1982) Kitchel (1982)and Stanley (1982) that no further comment isneeded here

Although Charles Darwin is generally regarded asthe flther of evolution theory (Darwin 1859) therewere many pre-Darwinian scientists who postulatedthat animals and plants had changed over long perishyods of time and that new types of species had arisenpoundiom pre-existing ones These early workers andDarwin himself identified many different pointswhich could be regarded as evidence for the originof rnodern species from pre-existing and moreprimitive ancestors All these are accepted todaythough rdined and added to Taxonomy as alwayslies at the heart of evolutionary thought and closelyintertwined with it is comparative anatomy Thefive-fingered or pentadactyl limb of higher verteshybrates for example has been modified in a varietyof ways The grasping hand of primates the flippersof marine mammals the wings of birds and batsthe hootS of horses - they all look dissimilar butarc all variants on a common theme Likewise thediversity in structure and function of the beaks ofthe Galapagos finches (Ceospiza) which Darwinencountered during the voyage of the Bc(~ghgt in1833 Icd him to say Seeing this gradation anddiversity in structure in one small intimately relatedgroup of birds one might really tancy that from anoriginal paucity of birds in this archipelago ollespecies had been taken and modified for difItrentends Geographical distribution was seen as imporshytant to evolutionary thought in other ways tooThus the existence of relict and isolated species(eg lungfish) in diHt~rent parts of the world surelyindicated an original widespread ancestral type asubsequent population collapse and restriction of a

Darwin the species and natural selection 27

few species to small areas only where each hadbecome adapted to its own environment

Darwin was particularly interested in selectivebreeding of animals and plants under domesticationHe realized that the present great variety of dogs andcattle had been produced in only a few thousandyears from only one or at most a few ancestral typesHe concluded that a great potential for descentwith modification must exist in all animals andplants which could be speeded up by such artificialbreeding This led on to the belief that similarprocesses though probably on a slower time scalehad operated in the wild state in other words natshyural selection Thus breeding experiments are thefoundation of classical genetics where the mechashynisrn of heredity is understood in tenns of its eHects

Darwin was also concerned with palaeontologybut he f()Und that the fossil record was somewhat ofa disappointment in supporting the case for evolushytionary change He had hoped to find evidenceof gradational change between animal species ofinilnitely numerous transitional links connectingancestors to descendants and of stratigraphicallyarranged series showing descent with modificationIn fact he did not find what he had expectedDarwin assumed that the imperfections of the rockrecord and the limitations of knowledge at that timewere the bctors responsible He was indeed partiallycorrect but to this point we shall return later

Of the pre-Darwinian evolutionists the mostprominent was the French naturalist Jean-BaptisteLamarck (1774-1829) who proposed long beforeDarwin that all living organisms had originated fromprimitive ancestors and that in the slow process ofsuch changes had becolTle adapted for living in particshyular environments rhe concept of such adaptationoriginated with Lamarck He appreciated that inorder to live animals have to be eHiciently adapted toall the physical and biological parameters of the envishyronments they inhabit In a sense of course an anishymal is all adaptation it has to be anatomicallyphysiologically and trophically adapted to its environshyment and it is critical to evolution theory to undershystand how such adaptations came to be

While appreciating the importance of adaptationhowever Lamarck linked his insight with someconcepts no longer believed to be tenable Hebelieved that adaptation had come about throughsome kind of internal driving force a vital sparkwhich made animals becolTle more complex He felt

28 Evolution and the fossil record

Inheritance and the source of variation

Figure 2 I Eukaryote cell structure with organelles

In the cells of all eukaryotes (all organisms except forviruses bacteria and cyanobacteria) there is anucleus (Fig 21) containing elongated thread-likebodies the chrOnlOSOllleS vvhich are made ofproshytein and deoxyribonucleic acid (DNA)

Goigiapparatus~

mitochondrion

smooth endoplasmic reticulum

the nature of variation and heredity vas largelyunknown so that his views on this were speculativeand insuffIcient f()r the th(01)7 to be seen to vvork

The pioneering work of the Austrian monkGregor Mendel in 1865 and of the later school ofTH Morgan which began in 1910 laid the founshydation for genetic experiment and theory It was thisthat supplied the necessary understanding of heredshyity essential to the amplification of Darwins theory

vacuole

1 Animal species reproduce more rapidly than isneeded to maintain their numbers Animal popushylations however though fluctuating tenel toremain ~table (Here he was influenced by theEnglishman Malthus who had vritten on thissubject some years earlier)

2 There must therefore be competition within andbetween species in the struggle for existence forf(Jod for living space and (within members of thesame specie~) for mates if the characters that indishyviduals bear are to be transmitted to the next genshyeration

3 Within species all animals vary and this variationis inherited

4 1n the struggle tlX life those individuals best fittedto survive in a particular environment are theones to live and to reproduce The others areweeded out in the intense competition Thef~1Vourablc characteristics that make such survivalpossible arc inherited by fllture generations andthe accumulation of different favourable characshyters leads to the separation of species well adaptedto particular cnvironrnents This is what Darwincalled natural selection

All this seems logical enough though Danvins earlycritics Mivart for instance argued that Darwin hadnot really shmvn how favourable characters wereactually accumulated only how those animals lessfitted to their environment failed to survive In thisthey were not unsound for the most serious weakshyness of the theory as presented by Danvin vas that

that ne-vv organs nlust arise from nci7 needs and thatthese acquired characters were inherited as in hisclassic postulate that the neck of the giraffe hadbecome longer in response to a need to reachleaves up on the tree The theory of inheritance ofacquired characters is not highly regarded novadaysand is generally lllltestable (although there issomc evidence of a kind of genetic feedback fromthe environment operating to produce apparentLunarckian changes) Darwin on the other handprovided a logical and testable theory plusmn()[ evolutionshyary change one that has stood the test of time andprovided a starting point for later developments

The flill title of Danvins major work of J859 -vvasOn the origin (( Ipecfes by nmms Cf natural seleaion orthe preservation (ffauollred races in the stnl~~le jc)r lifeThe main points of the theory are straightforward

The DNA molecule forms a long twisted spiralladder of which the uprights consist of alternateblocks of phosphoric acid and the pentose sugardeoxyribose whereas the rungs are matching pairsof relatively small units the nucleotide bases Thesebases in DNA arc adenine guanine thymine andcytosine They are attached to the pentose sugarunits and project inwards linking up together inpairs Adenine can only pair with thymine andcytosine with guanine

In the chromosome the DNA strands arearranged in discrete units the genes which arestrung together along the length of the chromoshysome and of which there may be several hundredper chromosome The genome is a term used todescribe the vvhole genetic complex These genesarc the primary units of heredity carrying thegenetic code which is involved in producing proshyteins and in directing the development and funcshytioning of the whole organism All the necessaryinformation for these ends is carried in the DNAand what is important is the sequence of the fournucleotide bases along its length Though thesef(xm a kind of alphabet consisting only of fourletters the number of possible combinations inwhich they can exist coding tor specific proteins isenormous This sequence of nucleotide basesdetermines the sequence in which any of the 20amino acids found in living organisms are strungtogether to make proteins It has been shown thatcombinations of three bases acting together code forparticular an11110 acids and there are 1nore thanenough possible combinations in this base-tripletsystem to make all the biogenic amino acids and tolink them up in the right order to make a specifreprotein

Proteins are synthesized not in the nucleus butat the ribosomes in the cellular cytoplasm and thismeans that all the information has to be transferredout of the nucleus to these sites of protein synthesisFor this to take place the nuclear DNA tlTSt proshyduces a single-stranded copy of itself nuclear RNAbut with uracil replacing thymine and ribose sugarreplacing deoxyribose Following this process oftranscription a further molecule (messengerRNA) is formed which moves out of the nucleuspresumably through pores in the nuclear membraneand attaches itself to the ribosome (This is not asimple process however for at this stage the genesthemscIves arc moditled It has been shown recently


that genes themselves are made of two kinds ofcomponents arranged in series These are exonswhich code for proteins and introns which donot When the nuclear DNA is transcribed tonuclear IZNA it retains the organization of the origshyinal DNA but when nuclear RNA is reprocessed tomessenger RNA the introns are lost and the exonsare spliced together This does not always take placein the original order however and such exon shutfling may be the basis of rapid evolution of proteinsthemselves in new combinations Provided thatthese are fLmctional new gene systems may arisethrough comparativcIy few such shuffling eventsand in short periods of time This is a newly undershystood phenomenon but may have important conseshyquences tor evolution theory)

When messenger RNA arrives at the surface of aribosome it does not form protein directly butthrough yet another imen11ediate molecule transferRNA and when this complex process is completethe result is a protein sequence coded for by thenuclear DNA the transfer RNA meanwhile returnshying to the cytoplasm

The understanding of protein synthesis has been am~or triumph for molecular biology but the moleshycular pathways that lead from genes to actual organsand characters are very complex and at presentlargely unknown How the proteins and other comshypounds which are produced are organized and Imiltup into functional organs and whole bodies remainsone of the main tasks for molecular biology for thefi-Iture Some progress has already been made it isnow known that S0111e genes arc structural andconcerned only with the synthesis of materialsothers are regulator genes which control andorganize the compounds and direct their buildingSuch genes release chemical products which start awhole host of complex reactions In some kindsof development the genes are switched on and offin particular sequence releasing products whichreact together in synthesizing complex moleculesStructural genes can be activated and deactivatedwhen needed evidently the initial stimulus for theswitching on of stmctural genes is given when asensor gene receives an appropriate stimulus

Simple organisms such as bacteria and tllllgi havesets of adjacent genes known as operons coding fora particular metabolic pathway These can beswitched otT and on together In higher organismshowever genes which control different parts of a




Fourth edition

bBlackwellScience







10 2008


ISBN 978-0-632-05238-7






Contents













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83

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100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

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147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

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Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole


















Fourth edition

bBlackwellScience







10 2008


ISBN 978-0-632-05238-7






Contents













xvxvi

1

333366889

101213131920202022232325

26262628303233343535373838

viii Contents













394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

















Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole






















10 2008


ISBN 978-0-632-05238-7






Contents













xvxvi

1

333366889

101213131920202022232325

26262628303233343535373838

viii Contents













394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

















Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole

















Contents













xvxvi

1

333366889

101213131920202022232325

26262628303233343535373838

viii Contents













394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

















Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















Contents













xvxvi

1

333366889

101213131920202022232325

26262628303233343535373838

viii Contents













394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

















Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















viii Contents













394041414243444445474950515153

5555555758585959606060616364646465686869697172737374747575767677787879

















Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
































Contents ix

83

858587888889909092939495969798989899

100lOO100

102102104104104lOS107107107108108109124128132135137138139139140

143143143143145

x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















x Contents
















147150154154155156156156156157

15815~

1581591591641671711751761771781791791831841~4

1~5

185188188188191191192192193194194194

197197199201201203203203














Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole





























Contents xi

203206209210213219220221222222224224226226229230238251255256256257

262262262263263263269270273276282285286288288289290290291291293293297298300301301

xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















xii Contents

















30130]3033043043053063073073113113J3313314314314315

318318318318320320320322324326329329329333335337338338339340340343344345345346

348348348348349















Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole






























Contents xiii

351351352354355357357357359360363365366367367370372372374377380382382383386387388388388392397400400400

406406409410412413415415416416416418420422424

xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















xiv Contents





Systematic index

General index

426426426426429429429430430431431431434434

435

443

Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















Preface


















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole























PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole
















PART ONE

General

Palaeontological

Concepts























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole






































~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole





































~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole



























~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole


















~~

(f)

core ---+j

(j)

Ironstone --~~~8B1



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole







































Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole



























Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole




















Taxonomy




































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole













































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole





































A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole

























A B c D















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole






























Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole




















Palaeobiology


















5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole























5000

if)

4000 aE

OCEANIC

ABYSSAL PLAIN--L--==-=-~~---10000

medn sea level

SLOPE

NERITIC

---7~-- __-~-----~~---

CONTINENTAL SHELF

~----- hightide

mean sea ievel

-- low tide

ABC





















FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole



































FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole

























FAUNAL PROVINCES






- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole

















- -

- Key


~ warm temperate

P-~= cold temperate

bull polar


-+- cold currents



















reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole


























reef-flat

100 m

















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole






























Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole



















Stratigraphy



























AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole


































AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole





















AeonEraa

Perioda

Epocho

AgeChron



Seriesa

StageChronozone













Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole




















Bibliography 23








































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole




































































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole































Bibliography 25


































Goigiapparatus~

mitochondrion




vacuole




































Goigiapparatus~

mitochondrion




vacuole





























Goigiapparatus~

mitochondrion




vacuole




















Goigiapparatus~

mitochondrion




vacuole
























Documents

Invertebrate Palaeontology - · PDF fileInvertebrate Palaeontology and Evolution E.N.K. Clarkson Professor ofPalaeontology DepartmentofGeology University ofEdinburgh Scotland Fourth